Towing systems and methods using magnetic field sensing

ABSTRACT

A magneto-elastically-based active force sensor, used with a tow coupling between a towed and a towing vehicle, which outputs a signal useful for determining forces acting on the coupling. The outputted force information may be provided by processor-enabled embedded software algorithms that take inputs from the force sensor and other sensors, may be used by one or more vehicle systems during operating of the vehicle, such as engine, braking, stability, safety, and informational systems. The force sensor includes directionally-sensitive magnetic field sensing elements inside the sensor, and shielding may be used around the sensors to reduce the influence of external magnetic fields on the sensing elements. The force sensor may be used with different tow coupling devices installed on different types of automobile cars and trucks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application that is based on andclaims the benefit of the filing date and disclosure of U.S. patentapplication Ser. No. 16/136,837, filed on Sep. 20, 2018, which is basedon and claims the benefit of the respective filing dates and disclosuresof U.S. Provisional Application No. 62/635,848, filed on Feb. 27, 2018,entitled “Magneto-elastic Based Sensor Assembly and Method”; U.S.Provisional Application No. 62/635,869, filed on Feb. 27, 2018, entitled“Tow Hitches With Magneto-elastic Sensing Devices and Methods”; U.S.Provisional Application No. 62/635,890, filed on Feb. 27, 2018, entitled“Towing System With Hitch Forces Sensing Method”; and U.S. ProvisionalApplication No. 62/677,378, filed on May 29, 2018, entitled “TowingSystem Using Magnetic Field Sensing Method,” the contents of each ofwhich are incorporated herein.

BACKGROUND OF THE INVENTION Field of Invention

The invention is related in general to systems and methods involving theuse of magnetic field sensors and magneto-elastic devices for measuringa load and outputting a signal indicative of a load force dynamicallyapplied to an object. The invention is also related to use of theforce-sensing apparatus in connection with a vehicle-trailer hitch ortow coupling. The invention is also related to methods for determining adirection and magnitude of the force vector on the hitch or a particularhitch component.

Description of Related Art

Tow coupling devices are popular accessories for owners of passengerautomobiles (cars and trucks) who tow trailers. These coupling devicesmay be purchased and installed in a new automobile, or purchased in theaftermarket and installed by owners after acquiring an automobile. Theautomotive and tow hitch industries classify trailer hitches accordingto various criteria. In one aspect, hitches are classified in one ofClass 1-5. Each class of hitch includes associated real-world standardssuch as minimum force load requirements, including at least longitudinaltension, longitudinal compression, transverse thrust, vertical tension,and vertical compression.

In many trailer hitch use cases, strain gauges are used for sensing aforce load on a hitch. Strain gauges, however, often require astructural weakening of the load-conducting elements. There is a needfor load measurements without compromising the structural stability ofthe measuring device. This is especially true for tow couplings.

Furthermore, there is a strong demand for smart tow couplings, e.g., forsystems providing at least the following: a load weight gauge (measuringthe tongue load of a tow coupling), a tow load weight shift alert, anunsafe trailer load distribution alert, a vehicle limit notification, anautomated trailer brake control (closed loop), a low/flat trailer tirenotification, a check trailer brake notification, a closed loop brakingcontrol, a vehicle shift control, an engine control, and a stabilitycontrol. These and other functions require the measurement of tow loadsand/or tongue loads at the tow coupling.

Prior art load measurement devices for tow couplings have significantshortcomings, e.g. the complexity of the measurement and controldevices, and the costs of the sensor assembly. Thus, there is a need fora tow coupling apparatus that may be purchased and installed in anautomobile that provides the above functions without weakening overtime.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, an improved magneto-elastic based sensorassembly is provided to effectively measure stress and strain in systemshaving a portion, which is subject to a mechanic load. The inventionalso provides a method of determining a direction of a load vectoracting on a magneto-elastic based sensor assembly.

In one aspect of the invention, a tow hitch assembly includes a hitchtube, a first part, a second part, a receiver tube, and first and secondload sensor pins 8, 9 connecting the first and second parts. The hitchtube is typically a longitudinally extending, round, oval, square, orother shape member for attaching to a vehicle, typically near the rearbumper of a passenger vehicle. Bolts or other fastening means may beused to attach the hitch tube to the vehicle.

The first part of the tow hitch assembly may be a bracket with two sideflange portions having through-holes: first and second through-holes onone flange, and third and fourth through-holes on the other, such thatthe first and third through-holes are axially aligned with each otherand the second and fourth through-holes are also axially aligned witheach other.

The second part may include a receiver tube connected to alongitudinally extending middle adapter member that fits between the twoflanges of the bracket when the hitch components are in an assembledstate. In one aspect, the adapter may be configured to include a frontportion that would be positioned in front of the hitch tube, and a backportion that would be positioned in back of the hitch tube, the frontand the back portions each having a through-hole axially aligned withthe through-holes on the bracket when the first and second parts are inan assembled state. In another aspect, the entirety of the adapter couldbe in front of the hitch tube, or behind the hitch tube, or in someother configuration.

In another aspect, the first and second load sensor pins 8, 9 areconfigured to sense forces applied to the receiver tube and othercomponents of the hitch assembly. One of the two load sensor pins 8, 9extends through the first and third through-holes of the bracket and oneof the through-holes of the adapter, and the other pin extends throughthe second and fourth through-holes of the bracket and a differentthrough-hole of the adapter to secure the first and second partstogether.

In another aspect, there is a gap of about 0.5 mm between the top of themiddle adapter member and the base portion of the bracket, and thethickness of the base portion of the bracket in the configuration shownis 8 mm. Alternatively, the thickness of the base portion of the bracketis about 10 mm, and the gap is about 5 mm between the top of the middleadapter member and the base portion of the bracket. Press-fit bushingscould be used, having a pre-determined radial thickness inserted intothe axially-aligned through-holes of the bracket.

In another aspect, during use of the assembled tow hitch, a force isapplied to the proximate end of a drawbar and transmitted to the frontpin. The output signals from magnetic field sensors associated with thefront pin may be received in a suitable software algorithm, for exampleone that is embedded on a circuit board having a suitable processorlocated inside the front pin. The receive output signals from thesensors, which may be indicative of the magnetic field/flux exhibited bythe front pin magneto-elastic active regions, may be used to determinethe forces.

In U.S. Pat. No. 9,347,845, owned by Methode Electronics, which isincorporated herein by reference in its entirety, a magneto-elasticsensor having a longitudinally extending shaft like member with at leastone magneto-elastically active region and a magnetic field sensor deviceis described. The longitudinally extending shaft like member is subjectto a load introducing mechanic stress in the member. The at least onemagneto-elastically active region is directly or indirectly attached tothe shaft like member. However, the at least one magneto-elasticallyactive region may also form a part of the member. Themagneto-elastically active region is arranged in such a manner that themechanic stress is transmitted to the active region. The region includesat least one magnetically polarized region such that the magneticpolarization becomes increasingly helically shaped as the applied stressincreases. The magnetic field sensor means or device is arrangedproximate the at least one magneto-elastically active region. Themagnetic field sensor means/device is further configured for outputtinga signal corresponding to a stress-induced magnetic flux, which emanatesfrom the magnetically polarized region. The sensor may be a magneticsensor device with at least one direction sensitive magnetic fieldsensor. This direction sensitive magnetic field sensor is configured fordetermination of a shear stress and/or of a tensile or compressivestress. In particular, the direction sensitive magnetic field sensor isarranged to have a predetermined and fixed spatial coordination with themember.

One object of the invention described herein, which is also described inEP17162429.9, owned by Methode Electronics and incorporated herein byreference in its entirety, is a sensor assembly for force sensing, theforce sensor being associated with a vehicle hitch assembly. Theimproved magneto-elastic based sensor assembly is useful for effectivelymeasuring stress and strain in systems having a portion, which issubject to a mechanic load. The invention provides a method ofdetermining a direction of a load vector acting on a magneto-elasticbased sensor assembly.

According to an aspect of the invention, a sensor assembly for forcesensing can include a first portion having a first and a secondthrough-hole. The sensor assembly can further include a second portionhaving a third and a fourth through-hole. The third and the fourththrough-hole can be positioned in correspondence to the first and thesecond through-holes.

The sensor assembly can further include a first pin and a second pin.The first pin can be arranged such that it extends through the first andthe third through-hole and the second pin can be arranged such that itextends through the second and the fourth through-hole, so as to couplethe first portion to the second portion. At least one out of the firstand the second pin can include at least one magneto-elastically activeregion that may directly or indirectly be attached to or form a part ofthe pin in such a manner that mechanic stress on the pin is transmittedto the magneto-elastically active region. The magneto-elastically activeregion can include at least one magnetically polarized region such thata polarization of the magnetically polarized region may becomeincreasingly helically shaped as the applied stress increases.

The sensor assembly can further include a magnetic field sensor means ordevice which may be arranged proximate the at least onemagneto-elastically active region. The magnetic field sensormeans/device may be configured to output a signal corresponding to astress-induced magnetic flux which may emanate from the magneticallypolarized region. The magnetic field sensor means/device may comprise atleast one direction sensitive magnetic field sensor which may beconfigured to determine a shear force in at least one direction. The atleast one direction sensitive magnetic field sensor may in particular bearranged to have a predetermined and fixed spatial coordination with thepin, wherein this pin may at least be partially hollow. The at least onedirection sensitive magnetic field sensor may be arranged inside aninterior of this pin.

By means of the sensor assembly, stress which is applied to a pin causedby a mechanic load can effectively be measured. The sensor assemblyaccording to aspects of the invention thus described overcomes thedrawback of the prior art solutions. In particular, the sensor assemblydoes not tend to drift with respect to the measurement values and isless error-prone.

According to another aspect of the invention, at least one out of thefirst and the second pin of the sensor assembly can comprise at leastone X-direction sensitive magnetic field sensor, which can be configuredto detect a force component Fx1 in a longitudinal direction X, and/or atleast one Z-direction sensitive magnetic field sensor, which can beconfigured to detect a force component Fz1 in a vertical direction Z.The longitudinal direction X can be defined by a direction oflongitudinal extension of the second portion. The vertical direction Zcan be substantially perpendicular to the longitudinal direction X andsubstantially perpendicular to the transversal direction Y oflongitudinal extension of the at least one pin.

According to another aspect of the invention, the first through-hole andthe third through-hole of the sensor assembly can be configured suchthat they encompass the first pin in a positive-fitting manner. Apositive-fitting manner of the fitting allows the pin to besubstantially rigidly fixed to the first portion and the second portionby the first and the third through-hole. This means that the pin hasalmost no play inside the first and third through-hole and that theaccuracy of the force measurement is advantageously increased comparedto a configuration in which the first pin has play inside the first andthe third through-hole.

According to another aspect of the invention, the first pin may becryogenically treated, such as by subjecting the entire first pin toliquefied nitrogen, thereby causing a reduction in the cross-sectiondimension of the pin. After super-cooling the first pin, it may bepositioned in the first and third through-holes and allowed to return toambient temperature. As the material in the pin warms up to ambienttemperature, the cross-section dimension will increase until the firstpin is substantially rigidly fixed in the first and third through-holes.

According to another aspect, the second pin of the sensor assembly maybe encompassed by the second through-hole in a positive-fitting mannerand the fourth through-hole may be configured such that the second pinmay have one additional degree of freedom of movement within the fourththrough-hole. The additional degree of freedom of movement allows thesecond pin to be insensitive with respect to shear forces acting in thedirection of the additional degree of freedom of movement. This meansthat the determination of the shear force along this direction canadvantageously be simplified since the shear effect occurs exclusivelyon the first pin.

According to another aspect, the second pin, like the first pin, may becryogenically treated, such as by subjecting the entire first pin toliquefied nitrogen, thereby causing a reduction in the cross-sectiondimension of the pin. After super-cooling the second pin, it may bepositioned in the second and fourth through-holes and allowed to returnto ambient temperature. As the material in the second pin warms up toambient temperature, the cross-section dimension will increase until thesecond pin is substantially rigidly fixed in the second and fourththrough-holes with the additional degree of freedom of movement notedabove.

According to another aspect, the additional degree of freedom ofmovement may extend in the longitudinal direction X. Since theadditional degree of freedom of movement corresponds to the longitudinaldirection X, the determination of the shear force along this directioncan advantageously be simplified.

According to another aspect, the first and/or the second pin of thesensor assembly can include a first magneto-elastically active regionand a second magneto-elastically active region. The first and the secondmagneto-elastically active regions may be directly or indirectlyattached to or form parts of the pin in such a manner that mechanicstress may be transmitted to the magneto-elastically active regions.Each magneto-elastically active region can include a magneticallypolarized region. Particularly, the magnetic polarization of the firstmagneto-elastically active region and the magnetic polarization of thesecond magneto-elastically active region may be substantially oppositeto each other. The magnetic field sensor means/device can include atleast one first direction sensitive magnetic field sensor which may bearranged approximate the first magneto-elastically active region. Themagnetic field sensor means/device may be configured to output a firstsignal corresponding to a stress-induced magnetic flux which may emanatefrom the first magneto-elastically active region. The magnetic fieldsensor means/device may include at least one second direction sensitivemagnetic field sensor which may be arranged approximate the secondmagneto-elastically active region. The magnetic field sensormeans/device may be configured to output a second signal correspondingto a stress-induced magnetic flux which may emanate from the secondmagneto-elastically active region. This way, the shear force canadvantageously be determined in two opposing directions therebyimproving the quality of the determination of the shear force. This“vice versa” configuration of the magnetic field sensors enables theshear directions to be determined by the magneto-elastically activeregions. For example, the directions may be distinguishable, if themeasurement data, which is acquired from the first direction sensitivemagnetic field sensor and the second direction sensitive magnetic fieldsensor, is differentially processed.

The differential evaluation of the signals advantageously doubles thesignal, which is correlated with the applied stress. Because thepolarization of the first and second magneto-elastically active regionis opposite to each other, theoretically possible external fields may becompensated. The sensor assembly according to this embodiment may bemore sensitive and less susceptible to errors.

According to another aspect of the invention, the first and/or thesecond pin of the sensor assembly can include at least one firstX-direction sensitive magnetic field sensor and/or at least one secondX-direction sensitive magnetic field sensor and/or at least oneZ-direction sensitive magnetic field sensor and/or at least one secondZ-direction sensitive magnetic field sensor. The at least oneX-direction sensitive magnetic field sensor may be configured to detecta force component Fx1 in the first magneto-elastically active region inthe longitudinal direction X of the second portion. The at least onesecond X-direction sensitive magnetic field sensor may be configured todetect a force component Fx2 in the second magneto-elastically activeregion in the longitudinal direction X of the second portion. The atleast one Z-direction sensitive magnetic field sensor may be configuredto detect a force component Fz1 in the first magneto-elastically activeregion in the vertical direction Z. The at least one second Z-directionsensitive magnetic field sensor may be configured to detect a forcecomponent Fz2 in the second magneto-elastically active region in thevertical direction Z. Advantageously, the shear force can be determinedin different directions being perpendicularly aligned with respect toeach other.

According to another aspect, the first pin of the sensor assembly caninclude the at least one Z-direction sensitive magnetic field sensor andthe at least one second Z-direction sensitive magnetic field sensor.Advantageously, the first pin can be configured to exclusively react ona shear force acting along the Z-direction.

According to still another aspect of the above invention, the first pinof the sensor assembly can include the at least one first X-directionsensitive magnetic field sensor, the at least one second X-directionsensitive magnetic field sensor, the at least one first Z-directionsensitive magnetic field sensor and the at least one second Z-directionsensitive magnetic field sensor and the second pin of the sensorassembly can comprise the at least one Z-direction sensitive magneticfield sensor and the at least one second Z-direction magnetic fieldsensor. Advantageously, the first pin can be configured to exclusivelyreact on the shear effect along the X-direction which simplifies theshear force evaluation, wherein the shear force along the verticalZ-direction is acting on both load sensor pins 8, 9.

According to another aspect, the first pin of the sensor assembly caninclude the at least one first X-direction sensitive magnetic fieldsensor, the at least one second X-direction sensitive magnetic fieldsensor, the at least one first Z-direction sensitive magnetic fieldsensor and the at least one second Z-direction sensitive magnetic fieldsensor, and the second pin of the sensor assembly can include the atleast one first X-direction sensitive magnetic field sensor, the atleast one second X-direction sensitive magnetic field sensor, the atleast one first Z-direction sensitive magnetic field sensor and the atleast one second Z-direction sensitive magnetic field sensor. This way,both load sensor pins 8, 9 are sensitive to all shear forces along thevertical Z-direction as well as along the longitudinal X-direction. Thefirst and the second pin advantageously can detect the differentcomponents of the shear force at different positions of the system.

The magnetic field sensor means/device may be configured fordetermination of a first component and a second component of the load,which is applied to the pin. In particular, the at least one firstX-direction sensitive magnetic field sensor and the at least one secondX-direction sensitive magnetic field sensor can form a first group ofsensors and the at least one first Z-direction sensitive magnetic fieldsensor and the at least one second Z-direction sensitive magnetic fieldsensor can form a second group of sensors. The first group of sensors issuitable for determination of a load component, which is directed alongthe X-axis. The second group of sensors senses a component of the load,which is substantially perpendicular to the first component along theZ-direction. Consequently, the direction and the value of the stress orforce, which is applied to the load sensor pins 8, 9, may be determinedfrom said components in this coordinate system.

According to another aspect, the second portion of the sensor assemblycan comprise a center wall which may extend in the longitudinaldirection X and the vertical direction Z. The third and the fourththrough-hole may also extend through the center wall. Advantageously,the center wall allows the first portion to be effectively affected bythe shear force at an additional point of action.

According to another aspect, the first and/or the second pin of thesensor assembly may be fixedly attached in a predetermined manner to thefirst portion. The first and/or the second pin can advantageously befixedly attached in all six degrees of freedom. This way, thedetermination of the shear forces is effectively possible since the loadsensor pins 8, 9 do not have play inside the through-holes of the firstportion.

According to another aspect, the first portion of the sensor assemblycan have a yoke-like shape. The yoke legs of the first portion cancomprise the first and the second through-holes. The second portion ofthe sensor assembly can have a tubular shape. The side walls of thesecond portion can comprise the third and fourth through-holes. Thedirection sensitive magnetic field sensor(s) may be configured to detectforce components of shear forces introduced into the load sensor pins 8,9 by the first portion and the second portion. Advantageously, ayoke-like shape of the first portion and a tubular shape of the secondportion allow the sensor assembly to be implemented in an elongatedjoint connection of two objects, whereas the load sensor pins 8, 9 arearranged in the through-holes and connect both objects.

According to another aspect, the first portion of the sensor assemblycan have a yoke-like shape. The yoke legs of the first portion cancomprise the first and the second through-holes. The center wall cancomprise the third and fourth through-holes. The direction sensitivemagnetic field sensor(s) may be configured to detect force components ofshear forces introduced into the load sensor pins 8, 9 by the firstportion and the second portion. In particular, the side walls of thesecond portion can comprise through-holes which may be larger than thethird and the fourth through-holes such that the shear forces may beintroduced into the load sensor load sensor pins 8, 9 by abutmentsurfaces of the first and the second through-holes in the yoke legs andabutment surfaces of the third and the fourth through-holes in thecenter wall. The abutment surfaces allow the transmission of powerbetween the first portion and the second portion to be configured in anadvantageous manner.

According to another aspect, a tow coupling can comprise a sensorassembly wherein the first portion is a hitch assembly that may beconfigured to be attached to a car chassis and wherein the secondportion may be a receiving tube which may be configured to receive adrawbar, alternatively a hitch bar or a ball mount of the tow coupling.Advantageously, the sensor assembly is configured to detect the forcesof a tow coupling of an automobile, which may be part of a land basedon-road or off-road vehicle.

According to another aspect, the first portion of the sensor assemblymay be a supporting yoke having two yoke legs. The yoke legs maycomprise recesses which are aligned in correspondence to each other andwhich represent the first and the second through-holes of the firstportion.

According to another aspect, the first portion of the sensor assemblymay be a supporting yoke having four yoke legs. The yoke legs maycomprise recesses which are aligned in correspondence to each other andwhich represent the first and the second through-holes of the firstportion.

According to another aspect, the sensor assembly dispenses with amechanical linkage or connection between the magnetic field sensor meansand the second portion. This eliminates sources of error, which resultfrom mechanic failure of this connection. The sensor assembly reliablyoperates even under extreme operating conditions. The drift of themeasurement values during long term measurement is reduced. The sensorassembly according to aspects of the invention is versatile in that itmay be applied to or integrated in nearly every tubular shaped portion,which may be for example a part of a hydraulic unit of a land-, marine-,rail- or air transport vehicle.

According to another aspect, the forces which are detectable by thesensor assembly are not exclusively restricted to shear forces whichoriginate from shear stress but may also originate due to tensile orcompressive stress acting on the magneto-elastically active region(s) ofthe first pin and/or the second pin of the sensor assembly. In otherwords, shear stress and normal stress may both induce a variation of thepolarization of the magnetically polarized region emanating from themagneto-elastically active region(s). This polarization may bedetectable by the magnetic field sensor means which may output a signalcorresponding to a stress-induced magnetic flux towards the polarizationdirection sensitive magnetic field sensor that may be configured todetermine the acting force. Consequently, the magneto-elastically activeregion may be sensitive to all stress types. The embodiment mayparticularly be suitable, if the pin is exposed to only one single typeof stress.

According to another aspect, the direction sensitive magnetic fieldsensors L may be one of a Hall-effect, magneto-resistance,magneto-transistor, magneto-diode, MAGFET field sensors or fluxgatemagnetometer. These aspects advantageously apply to all embodiments ofthe invention.

According to another aspect, any hydraulic piston, crane application,car and other various applications incorporating bolts and load sensorpins 8, 9, where shear forces may be applied, may be equipped with thesensor assembly according to aspects of the invention. Traditionally,shear force sensors using strain-gauges are designed in that they getintentionally weaken to provide enough deformation so as to allow ameasurement of the applied loads. The magneto-elastically active regionof the sensor assembly, however, provides the possibility to design thebolt without weaken locations and significantly higher overloadcapability. The load pin having the integrated magneto-elasticallyactive region provides the possibility to detect shear forces in loadsensor pins 8, 9, screws, bolts etc.

According to another aspect, a method of determining a direction of aload vector is provided. Within said method, a sensor assembly accordingto aspects of the invention is provided. In other words, a sensorassembly is provided which can comprise a first portion having a firstand a second through-hole. The sensor assembly can further comprise asecond portion having a third and a fourth through-hole. The third andthe fourth through-hole can be positioned in correspondence to the firstand the second through-hole. The sensor assembly can further comprise afirst pin and a second pin. The first pin can be arranged such that itextends through the first and the third through-hole and the second pincan be arranged such that it extends through the second and the fourththrough-hole, so as to couple the first portion to the second portion.At least one out of the first and the second pin can comprise at leastone magneto-elastically active region that may directly or indirectly beattached to or form a part of the pin in such a manner that mechanicstress on the pin is transmitted to the magneto-elastically activeregion. The magneto-elastically active region can comprise at least onemagnetically polarized region such that a polarization of themagnetically polarized region may become increasingly helically shapedas the applied stress increases. The sensor assembly can furthercomprise a magnetic field sensor means which may be arranged approximatethe at least one magneto-elastically active region. The magnetic fieldsensor means may be configured to output a signal corresponding to astress-induced magnetic flux which may emanate from the magneticallypolarized region. The magnetic field sensor means may comprise at leastone direction sensitive magnetic field sensor which may be configured todetermine a shear force in at least one direction. The at least onedirection sensitive magnetic field sensor may in particular be arrangedto have a predetermined and fixed spatial coordination with the pin,wherein this pin may at least be partially hollow. The at least onedirection sensitive magnetic field sensor may be arranged inside aninterior of this pin.

Furthermore, within the method according to another aspect, the firstpin and the second pin may be exposed to a load. Measurement data of theat least one direction sensitive magnetic field sensor may be processedso as to determine a shear stress and/or a tensile or compressive stressthat is applied by the second portion and the first portion to the firstand/or second load sensor pins 8, 9.

In particular, a direction of a force F may be determined from themeasurement data on the one hand and the predetermined and known spatialcoordination between the direction sensitive magnetic field sensor(s),the first pin, the second pin and the point of load. The force F isapplied to the sensor assembly via the second portion.

Same or similar advantages which have been already mentioned withrespect to the sensor assembly having a magneto-elastically activeregion according to aspects of the invention apply in a same or similarway to the method of determining a direction of the load vector and willbe not repeated.

Devices and methods related to magnetizing a cylindrical shaft, pin, orsimilar shaped object, and using magnetic field sensors positionedproximate to the same for detecting a magnetic flux emanating from theobject and other magnetic fields, are disclosed in one or more of thefollowing patents owned by Methode Electronics, the entire contents anddisclosures of which are incorporated herein by reference: U.S. Pat. No.6,490,934 (“Circularly magnetized non-contact torque sensor and methodfor measuring torque sing the same”); U.S. Pat. No. 6,553,847(“Collarless circularly magnetized torque transducer and method formeasuring torque using the same”); U.S. Pat. No. 6,904,814 (“Magnetictorque sensor system”); U.S. Pat. No. 7,140,258 (“Magnetic-basedforce/torque sensor”); U.S. Pat. No. 8,087,304 (“Magneto-elastic torquesensor with ambient field rejection”); U.S. Pat. No. 8,578,794;(“Magneto-elastic torque sensor with ambient field rejection”); and U.S.Pat. No. 8,893,562 (“System and method for detecting magnetic noise byapplying a switching function”).

In many of the above references, a magneto-elastic torque sensor isdescribed, in which an output signal indicative of a force applied to amember is provided. The sensor includes a first magneto-elasticallyactive region in the member, the region being ferromagnetic,magnetostrictive magnetically polarized in a single circumferentialdirection and possessing sufficient magnetic anisotropy to return themagnetization in the region to the single circumferential direction whenthe applied torque is reduced to zero, whereby the ferromagnetic,magnetostrictive region produces a magnetic field varying with thetorque. Magnetic field sensors are mounted proximate to theferromagnetic, magnetostrictive region to sense the magnetic field atthe sensors and provide the output signal in response thereto.

Apparatus and methods related to strain-induced magnetic anisotropy tomeasure the tension or compression present in a plate-like object aredescribed in US20150204737 (“Magneto-elastic sensor”), owned by MethodeElectronics, the entire content and disclosure of which are incorporatedherein by reference. The device includes an annular region of a plate ismagnetized with a circumferential magnetization. Magnetic field sensorsare then placed near this magnetized band at locations where themagnetization direction is non-parallel and non-perpendicular to theaxis of tension. The strain-induced magnetic anisotropy caused bytension or compression then produces a shift in the magnetizationdirection in the plate regions near the field sensors, thereby causingmagnetic field changes which are detected by the magnetic field sensors.The magnetic field sensors are connected to an electronic circuit whichoutputs a voltage signal which indicates the tension or compression inthe plate.

According to another aspect, an embedded software program is used toreceive signals from various sensors and output a signal containinginformation useful in determining or assessing a load weight gauge(measuring the tongue load of a tow coupling), a tow load weight shiftalert, an unsafe trailer load distribution alert, a vehicle limitnotification, an automated trailer brake control (closed loop), alow/flat trailer tire notification, a check trailer brake notification,a closed loop braking control, a vehicle shift control, an enginecontrol, and a stability control.

According to another aspect, shielding material or a shielding device ormultiple shielding devices may be used to shield the load sensor pins 8,9 from the effects of external magnetic sources, such as nearbypermanent magnets. In one embodiment, a flux directly may be used todirect external magnetic fields to minimize or reduce their effect onthe load sensor pins 8, 9 and the output signal from the load sensorpins 8, 9.

According to another aspect, the load sensor pins 8, 9 output one ormore signals to one or more microcontroller units. The microcontrollersare adapted to processing the signals and providing processed signals toa vehicle onboard control system via the vehicle's bus network. Theprocessed signal may include information related to a comparison of theload pin forces to one or more threshold forces and instructional datafor corrective actions to be taken by one or more vehicle controlsystems in response thereto.

In another aspect, the load sensor pins 8, 9 and other components of thetow coupling apparatus may be used to measure a sprung weight of atowing or towed vehicle by measuring the sheer forces on the load sensorpins 8, 9 caused by the weight on the vehicle producing a force on theload sensor pins 8, 9.

The present invention provides additional advantageous features relatedto magneto-elastic sensors for measuring forces, especially loadsapplied to one or more components of a vehicle hitch assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, schematic diagram of the outside of a loadsensor pin for use with a tow coupling apparatus;

FIG. 2 is a simplified, schematic diagram of the outside of another loadsensor pin for use with a vehicle tow coupling apparatus;

FIG. 3 is a simplified, perspective, exploded view diagram of some ofthe components of a “front” load sensor pin;

FIG. 4 is a simplified perspective view schematic diagram of a multi-pinelectrical connector for use with the load sensor pin of FIG. 3;

FIG. 5 is a simplified, cross-sectional, plan view diagram of the loadsensor of FIG. 3;

FIG. 6 is a simplified, perspective exploded view diagram of some of thecomponents of a “back” load sensor pin;

FIG. 7 is a simplified, cross-sectional, plan view diagram of the loadsensor of FIG. 6;

FIG. 8 is a simplified, partial, cross-sectional, plan view diagram ofthe load sensor of FIG. 6;

FIG. 9 is a simplified, partial, cross-sectional, plan view diagram ofthe “front” and “back” load sensor pins of FIGS. 3 and 6 and some of thecomponents of a tow coupling apparatus;

FIG. 10A is a simplified, cross-sectional view drawing of another aspectof a load sensor pin;

FIG. 10B is a simplified, partial, cross-sectional, perspective viewdiagram of the load sensor pin of FIG. 10A;

FIG. 10C is a simplified, partial, perspective view diagram of anotheraspect of a load sensor pin of FIG. 10A;

FIG. 10D is a simplified, end view diagram of yet another aspect of theload sensor pin of FIG. 10A;

FIG. 11A is a simplified, schematic diagram of the load sensor pin ofFIG. 2 with a shielding device;

FIG. 11B is a simplified, exploded, perspective view diagram of thecomponents of a load sensor pin showing a printed circuit board betweentwo elongated magnetic field shielding members;

FIG. 12A is a simplified, partial, perspective view diagram of some ofthe components of a load sensor pin having a secondary magnetic fieldsensor;

FIG. 12B is another simplified, partial, perspective view diagram ofsome of the components of the load sensor pin of FIG. 12A;

FIG. 13 is a simplified, partial, perspective view diagram of some ofthe components of a tow coupling apparatus showing front load sensor pin8 and back load sensor pin 9;

FIG. 14 is another simplified, partial, perspective view diagram of thecomponents of the tow coupling apparatus showing front load sensor pin 8and back load sensor pin 9;

FIG. 15 is a simplified, partial, cross-sectional, end view diagram ofthe components of the tow coupling apparatus of FIG. 13;

FIG. 16 is another simplified, partial, cross-sectional, end viewdiagram of the components of the tow coupling apparatus of FIG. 13;

FIG. 17A is a simplified, partial, perspective view diagram of the towcoupling apparatus of FIG. 14;

FIG. 17B is a close-up simplified, partial, perspective view diagram ofthe apparatus of FIG. 14;

FIG. 18A is a simplified, partial, perspective view diagram of some ofthe components of the tow coupling apparatus of FIG. 14 showing a firstload case;

FIG. 18B is another simplified, partial, perspective view diagram ofsome of the components of the tow coupling apparatus of FIG. 14 showinga different load case;

FIG. 19A is a simplified, partial, perspective view diagram of thevehicle tow coupling apparatus of FIG. 14 with a shielding device;

FIG. 19B is a semi-transparent diagram of FIG. 19A;

FIG. 19C is another view of the shielding device of FIG. 19A;

FIG. 20 is a simplified, side view diagram of the tow coupling apparatusof FIG. 14 showing another load case;

FIG. 21 is a simplified, side view diagram of a tow coupling apparatusand vehicle components;

FIG. 22 is a simplified, perspective view diagram of one component of atow coupling apparatus showing upper and lower load sensor pins 8, 9;

FIG. 23 is a simplified, perspective view diagram of the couplingcomponents of a vehicle tow coupling apparatus;

FIG. 24 is a simplified, perspective, exploded view diagram of some ofthe components of another tow coupling apparatus;

FIG. 25 is another simplified, perspective, exploded view diagram of themodified components of the tow coupling apparatus of FIG. 24;

FIG. 26 is a simplified, perspective view diagram of the components ofthe tow coupling apparatus of FIG. 24;

FIG. 27 is a simplified, process flow diagram of a method ofcryogenically treating a load sensor pin;

FIG. 28A is a simplified, partial, exploded, perspective view diagram ofa tow coupling apparatus including load sensor pins 8, 9;

FIG. 28B is another simplified, partial, exploded, perspective viewdiagram of the tow coupling apparatus of FIG. 28A;

FIG. 29 is a simplified, exploded, perspective view diagram of some ofthe components of the vehicle tow coupling apparatus of FIG. 28A;

FIG. 30 is a simplified, partial, cross-sectional view diagram of thetow coupling apparatus of FIG. 28A;

FIG. 31A is another simplified, plan view diagram of a load sensor pin;

FIG. 31B is an end view diagram of the load sensor pin of FIG. 31A;

FIG. 32A is a simplified, partial, axial, cross-sectional view diagramof a load sensor pin for use in the tow coupling apparatus of FIG. 31A;

FIG. 32B is a simplified, partial, cross-section, end view diagram ofthe load sensor pin of FIG. 32A;

FIG. 33 is simplified, partial, cross-sectional view diagram of a loadsensor pin for use in a tow coupling apparatus;

FIG. 34 through FIG. 41 are simplified, schematic, top view diagrams ofa portion of a tow coupling apparatus showing various simplified loadcases;

FIGS. 42A through 42AA are perspective view diagrams of tow hitchassemblies, towed or towing vehicles, and weight sensing assembliesusing one or more load sensor pins at various force transmittingcomponents.

DETAILED DESCRIPTION OF THE INVENTION

Several preferred embodiments of the invention are described forillustrative purposes, it being understood that the invention may beembodied in other forms not specifically described below and/or shown inthe drawings.

For reference purposes, a Cartesian coordinate system is used todescribe certain features, components, and directions, and unlessotherwise stated or shown in the figures otherwise, the x-axis generallyrefers to a longitudinal direction, the y-axis generally refers to atransverse direction that is perpendicular to the x-axis, and the z-axisgenerally refers to a vertical direction that is perpendicular to aplane formed by the x- and y-axes.

Turning first to FIG. 1, shown therein is a simplified, schematicdiagram of a load sensor pin 8 (and similar load sensor pin 9; as bestseen in FIG. 5) for use with a tow coupling apparatus, one that isadapted to being attached to a towing vehicle (e.g., passengerautomobile car or truck; not shown) at/near the back/rear bumper of thetowing vehicle. The load sensor pin 8 referred to here is a “front” loadsensor pin given its relative position with respect the load sensor pin9; that is, in one embodiment, the load sensor pin 8 is installed in thetow coupling apparatus such that it would be closer to the front of atowing vehicle when the tow coupling apparatus is mounted to the towingvehicle, whereas the load sensor pin 9 is behind the load sensor pin 8and thus would be closer to the back of the towing vehicle. The relativepositions of the load sensor pins 8, 9 may be different than thearrangement shown in the drawings, depending on the particular type oftow coupling application.

The load sensor pins 8, 9 may include a center portion 120 andlongitudinally spaced apart end portions 130 a, 130 b on either side ofthe center portion 120. Between the center portion 120 and the endportion 130 a is a magneto-elastically active portion 21 bordered byjoints 142 a and 144 a (the same features are shown on the other side ofthe center portion 120). The magneto-elastically active portion 21 istreated in such a way that a longitudinally-extending portion of thesurface of the load sensor pins possess a magneto-elastic active regionfor producing an external magnetic field/flux, as further describedbelow.

Each of the load sensor pins 8, 9 are preferably hollow shafts having awall thickness ranging from about 0.2 mm at its thinnest to about 3 mmat its thickest along its longitudinal dimension, but the actual wallthickness may be determined based on a particular needs of theapplication in which the load sensor pins 8, 9 are used. The outersurface of the load sensor pins 8, 9 may have portions that are round orflat.

The dimension 122, which spans a portion of the center portion 120 andthe magneto-elastically active portion 21 (as well as a portion of thecenter portion 120 and the magneto-elastically active portion 22), mayvary by application. The dimension 124, which is a diameter of the endface of the end portion 130 b of the load sensor pin 8, 9 (as well as adiameter of the end face of the end portion 130 a of the load sensor pin8, 9) may also vary as necessary. The dimension 126, which is the widthof the magneto-elastically active portions 22 (as well as the width ofthe magneto-elastically active portions 21) may be about 8 mm to about24 mm. The dimension 128, which is a diameter of the inner wall surfaceof the load sensor pin 8, 9 at the ends of the end portion 130 a of theload sensor pin 8, 9 (as well as the a diameter of the inner wallsurface of the load sensor pin 8, 9 at the ends of the end portion 130 bof the load sensor pin 8, 9) may also vary by application.

All or some of the center portion 120 and the end portions 130 a, 130 bmay be made from non-magnetic materials to keep near field magneticfield generating sources, such as a permanent magnet, magnetized wrench,motor, or solenoid, at a minimum distance from the load sensor pins 8, 9to reduce or eliminate (below detection) the path of magnetic fieldsfrom those types of sources. This would limit or eliminate the effectthese near field sources have on the force dependent field measurementsproduced by the magneto-elastically active portions 21, 22 of the loadsensor pins 8, 9.

Another way to reduce the influence of external magnetic fields in/onthe load sensor pins 8, 9 is to have only the shear areas of the loadsensor pins 8, 9 made of ferromagnetic material. That is, it is notnecessary for the rest of the load sensor pins 8, 9 to be made from aferromagnetic material, and in some instances it is rather undesirableas such materials only act as a flux director for channeling externalmagnetic fields towards the magnetic field measurement coils (notshown).

The load sensor pins 8, 9 are further described in Applicant's Europeanpatent application EP17162429.9, which is incorporated herein byreference.

Turning now to FIG. 2, shown therein is a simplified, schematic diagramof another aspect of the load sensor pin 8, 9 of FIG. 1 in which thecenter portion 120 is divided into two separate center portions 120 a,120 b, separated by a joint. In this embodiment, all or some of thecenter portions 120 a, 120 b, along with their adjacent magneto-elasticactive portions 21, 22, are made from a material and/or treated asdescribed above in such a way that they produce an external magneticfield/flux.

To construct the load sensor pins 8, 9 as shown in FIG. 1 and FIG. 2,the different materials of the various portions could be welded together(e.g. using friction welding). Another possibility would be to take aload sensor pin 8,9 constructed of austenitic stainless steel(non-magnetic) and transform the shear areas to a martensitic materialthrough the process of cold working thus forming the magneto-elasticactive portions 21, 22.

Turning now to FIG. 3 and FIG. 5, shown therein are a simplified,perspective and cross-sectional, and exploded view diagrams of some ofthe components of the first load sensor pin 8. As shown, the load sensorpin 8 includes a retaining clip 302, a printed circuit board 304, a setof connector pins 306, a support member 308 having a pin connectorhousing 311 (as also shown in FIG. 4) on a terminating end, and a pairof sealing rings 310. The retaining clip 302 is used to fix the supportmember 308 in a way that minimizes movement after it is fixed in itsfinal assembled state. The printed circuit board 304 may have one ormore (such as four) magnetic field sensors (described below) mountedthereon each with leads for connecting to the set of connector pins 306.The printed circuit board 304 includes a suitable processor, memory, andembedded software (not shown). The set of connector pins 306 includeinsert molded pins on one end for extending up and through pre-drilledthrough-holes on the printed circuit board 304 for connecting to the oneor more magnetic field sensors and other circuit components on theprinted circuit board 304. The other end of the set of connector pins306 terminate with suitable latch-type or friction fit-type pins thatconnect with a suitable connector of an electrical harness (as best seenin FIG. 12A). The sealing rings 310 are used to prevent anything fromentering the interior of the load sensor pin 8.

Turning now to FIG. 6 and FIG. 7, shown therein are simplified,perspective and cross-sectional, exploded view diagrams of some of thecomponents of the second load sensor pin 9. As shown, the load sensorpin 9 includes a retaining clip 602, a printed circuit board 604, a setof connector pins 606, a support member 608, a pair of sealing rings610, and a connector housing 611. The retaining clip 602 is used to fixthe support member 608 after it is fixed in its final assembled state toprevent movement. The printed circuit board 604 may have one or more(such as eight) magnetic field sensors (not shown) mounted thereon eachwith leads for connecting to the connector pins 606, which in turn leadto a flat, circular-shaped printed circuit board. The printed circuitboard 604 includes a suitable processor, memory, and embedded software(not shown). A micro ribbon or cable (as shown in FIG. 8) connects theprinted circuit board 604 and a circular printed circuit board. Theflat, circular-shaped printed circuit board connects to a four-pinconnector inside the connector housing 611. The sealing rings 610 areused to prevent anything from entering the interior of the load sensorpin 9.

Turning now to FIG. 9, shown therein is a simplified, partial,cross-sectional, plan view diagram of the “front” and “back” load sensorpins of FIGS. 3 and 6 and some of the components of a tow couplingapparatus as they could be employed in connection with a tow couplingapparatus (for ease of reference, the two load sensor pins are shownwith load sensor pin 9 on top of load sensor pin 8). As shown, thecenter portions 120 of the load sensor pins 8, 9 are rigidly fixedinside the through-holes of a bracket 902 that generally surrounds theload pins 8, 9. The end portions 130 a, 130 b of the load sensor pins 8,9 are further rigidly fixed inside corresponding through-holes of theyoke-like projections 904 a, 904 b of a generally U-shaped adapter 904(supporting yoke) that surrounds the bracket 902. Bushings 906 a, 906 b,906 c, 906 d surround respective portions of the load sensor pin 9, andbushings 908 a, 908 b, 908 c, 908 d surround respective portions of theload sensor pin 8. The bushings may be brass or some other material. Insome embodiments, no bushings are used between the end portions 130 a,130 b of the load sensor pins 8, 9 and the respective through-holes ofthe side yoke-like projections 904 a, 904 b of the adapter 904. In thatembodiment, the load sensor pins 8, 9 are in direct contact with thewalls of the through-holes.

The load sensor pins 8, 9 are made from one or more materials, inaddition to ferromagnetic materials, and are constructed in such a waythat they are suitable for forming the magneto-elastic active regions21, 22. The chosen materials and construction of the various portions ofthe load sensor pins 8, 9 should be such that the nature of the shaft ofthe load sensor pins 8, 9 is one that is elastically deformable. Thisprovides for the relative movement between the center portions 120(caused by a force imparted by the bracket 902 on the center portions120) and the rigidly fixed end portions 130 a, 130 b (maintained in astationary position by the adapters 904). The eccentric deformationcaused by forces imparted on the load sensor pins 8, 9 causes themagneto-elastic active regions 21, 22 to produce the external magneticfield/flux as previously described.

Turning now to FIGS. 10A through 10D, shown therein are a simplifiedcross-sectional, perspective view drawings of others aspects of a loadsensor pin 8, 9. In FIG. 10A, a load sensor pin 8 has a length along itslongitudinal direction such that the slot 312 (and slot 612) forreceiving the retaining clip 302 is outside the bushing 908 d (906 d inthe case of the load sensor pin 9). In one embodiment, the slots 312,316 may be about 1.5 mm wide and have an inner diameter of about 24 mm,and they may be about 4 mm from the end of the load sensor pin 8. InFIG. 10C, the retaining clip 302 includes a raised flange or post 302 athat fits inside a pole yoke opening 314 as best seen in FIG. 10B toprevent the retaining clip 302 from slipping out of its slot 312(similarly, the retaining clip 602 includes a raised flange or post toprevent the retaining clip 602 from slipping out of its slot 612). Thepole yoke opening 314 may extend through the wall of the load sensor pin8, for example to accept a raised flange or post 302 a having about a 2mm length. In FIG. 10D, one possible configuration for the retainingclips 302, 602 is shown.

Turning now to FIG. 11A and FIG. 11B, shown therein is a simplified,schematic diagram of one of the load sensor pins 8, 9 of FIG. 2 inside ashielding device 910, and a simplified, exploded, perspective viewdiagram of the components of a load sensor pin 8, 9 showing a printedcircuit board 304, 604 between two elongated magnetic field shieldingmembers 912 a, 912 b, respectively. In FIG. 11A, the shielding device910 may be a box or other shape and is made using materials with highmagnetic permeability, which shunts an external magnetic field byoffering a path of low resistance to the field and thereby minimizing oreliminating the influence of the field on the force dependent fieldmeasurements produced by the load sensor pins 8, 9. In FIG. 11B, theshielding members 912, 912 b also help to minimize or eliminate theinfluence of the field on the force dependent field measurementsproduced by the load sensor pins 8, 9. Shielding effects are furtherdescribed in Applicant's U.S. Pat. No. 8,578,794 (Magneto-elastic TorqueSensor with Ambient Field Rejection), which is incorporated herein byreference in its entirety.

Turning now to FIG. 12A, shown therein is a simplified, partial,perspective view diagram of some of the components of a load sensor pinhaving a secondary magnetic field sensor 916. FIG. 12B shows anothersimplified, partial, perspective view diagram of some of the componentsof the load sensor pin of FIG. 12A. The components of one of the loadsensor pins 8, 9, is shown in which its respective printed circuit board304, 604 includes primary magnetic field sensors 914 a, 914 b and asecondary magnetic field sensor 916. The secondary magnetic field sensor916 may be a 3-axis compass sensor (either standalone or as part of a9-axis sensor), which is used to detect the presence of externalmagnetic fields in the case that the shielding elements described aboveare not effective in eliminating all external fields. Informationoutputted by the secondary magnetic field sensor 916 could be used toperform compensation calculations on the force measurements. Inaddition, each of the load sensor pins 8, 9 could include extra sensingcoils arranged in a way to minimize the influence of external magneticfields on the measurement of the forces by the primary magnetic fieldsensors 914 a, 914 b.

The effects of external magnetic fields may also be taken into accountby computational means using a suitable algorithm, which may beprocessed by embedded software on the printed circuit board 304, 604, orin a separate electronics module 980 connected to the printed circuitboard 304, 604 via cable connector 982. Due to the mechanicalconfiguration of a sensor system assembly (especially ones with two ormore load sensor pins 8, 9 or two sensing planes), there can be certainrelationships between the forces detected by the load sensor pins 8, 9that have to be fulfilled. An external field is likely to cause animplausible relationships/combination of individual forces measured,which an algorithm could detect and compensate for.

Turning now to FIG. 13, shown therein is a simplified, partial,perspective view diagram of some of the components of a tow couplingapparatus showing front load sensor pin 8 and back load sensor pin 9 forcoupling a towing vehicle to a towed vehicle. As shown, the tow couplingapparatus includes a bracket 902 attached to a receiver tube 920, and agenerally U-shaped adapter 904 attached to a hitch tube 922.

The hitch tube 922 is a longitudinally extending, round, oval, square,or other shape member of the type typically used to attach to a towingvehicle (not shown) near the rear bumper of the towing vehicle. Thehitch tube 922 is the component that couples the tow coupling apparatusto the towing vehicle to transmit force (generated by the towingvehicle's engine) to a towed vehicle (not shown), such as a trailer.Bolts or other fastening means may be used to securely attach the hitchtube 912 to the towing vehicle.

The adapter 904 has two side yoke-like projections 904 a, 904 bextending approximately 90-degrees from a base portion such that theyare parallel to each other. Each side wall includes through-holes: firstand second through-holes 924-1, 924-2 on the side wall 904 b, and thirdand fourth through-holes 924-3, 924-4 on the side wall 904 a, such thatthe first and third through-holes 924-1, 924-3 are axially aligned witheach other, and the second and fourth through-holes 924-2, 024-4 arealso axially aligned with each other. The end portions 130 a, 130 b ofthe load sensor pins 8, 9 are rigidly fixed inside the through-holes ofthe side yoke-like projections 904 a, 904 b of the adapter 904, in somecases using collars or bushings, that surrounds the bracket 902 asshown.

The bracket 902, which may be a single member or two separate membersarranged on front and back sides of the hitch tube 922, fits between thetwo side yoke-like projections 904 a, 904 b of the adapter 904 when thetow coupling apparatus components are in an assembled state. The bracket902 includes a front portion and a back portion. The front portion andthe back portion each includes a through-hole (not shown) axiallyaligned with the through-holes on the adapter 904 when the componentsare in the assembled state. Through-holes on the front and back portionsof the adapter 904 may be slightly larger than the through-holes 924-1,924-2, 924-3, 924-4 such that shear forces transmitted from the receivertube 920 are introduced into the load sensor pins 8, 9 by abutmentsurfaces of the through-holes 924-1, 924-2, 924-3, 924-4 in the adapter904 and abutment surfaces of the through-holes in the bracket 902.

The bracket 902 and the adapter 904 are each made of a material selectedfrom suitable materials that resist deforming over time under a range ofexpected applied forces.

There may a gap of about 0.5 mm between the top of the bracket 902 andthe connecting base portion of the adapter 904 (the portion thatconnects to the hitch tube 922). The thickness of the base portion ofthe adapter 904 in the configuration shown may be 8 mm. Alternatively,the thickness of the base portion of the adapter 904 may be 10 mm, whichmay be achieved, for example, by modifying the placement of the variousthrough-holes and changing other dimensions of the adapter 904.

Turning now to FIG. 14, shown therein is another simplified, partial,perspective view diagram of the components of the tow coupling apparatusshowing front load sensor pin 8 and back load sensor pin 9. In thisembodiment, an alternative approach to using the adapter 904 is shown.Instead of a one-piece adapter 904 with a base portion, two spaced apartside yoke-like projections 904 a, 904 b, and through-holes 924-1, 924-2,924-3, 924-4, the alternative adapter includes four separate adapters904-1, 904-2, 904-3, 904-4 each separately connected directly to a hitchtube 922 as shown.

Turning now to FIG. 15 and FIG. 16, shown therein are simplified,partial, cross-sectional, end view diagrams of the components of the towcoupling apparatus of FIG. 13. As shown in FIG. 15, the lower edge ofthe side yoke-like projections 904 a, 904 b of the adapter 904 include abeveled edge such that there is a gap of about 7 mm between the beveledge and the closest edge of the receiver tube 920. There is also a gapof about 0.5 mm between the upper edge of the bracket 902 and the baseportion of the adapter 904 (the thickness of the base portion here couldbe about 8 mm or as needed to provide rigidity for the side yoke-likeprojections 904 a, 904 b). As shown in FIG. 16, the gap between theupper edge of the bracket 902 and the base portion of the adapter 904 isincreased from 0.5 mm to 5 mm (the thickness of the base portion herecould be about 10 mm to provide additional rigidity for the sideyoke-like projections 904 a, 904 b). Various other dimensions(thickness) of the base portion of the adapter 904 are also contemplatedand may be suitable for different expected forces or loads on the towcoupling apparatus components. Also shown are press-fit bushings havinga pre-determined radial thickness inserted into the axially-alignedthrough-holes of the bracket.

Turning now to FIG. 17A and FIG. 17B, shown therein are simplified,partial, perspective view diagrams of the tow coupling apparatus of FIG.14. Specifically, a drawbar 930 is shown inserted into the receiver tube920 and may be fastened in the receiver tube 920 with a connecting pin(not shown). As described below, the drawbar 930 is the connectionmember between the tow coupling apparatus and the towed vehicle (e.g.,trailer), and thus is a force-transmitting member that can be monitoredby use of the load sensor pins 8, 9 as previously described.

In particular, FIG. 18A is a simplified, partial, perspective viewdiagram of some of the components of the tow coupling apparatus of FIG.14 showing a first load case in which a force is applied to theproximate or free end of the drawbar 930 (i.e., the end closest to theviewer). This applied force will be transmitted to the distal or pinnedend of the drawbar 930 inside the receiver tube 920. That is, the forcecorresponding to the transmitted force at the distal end of the drawbar930 by the towed vehicle may be transmitted to the receiver tube 920.That force then acts on the bracket 902 attached to the receiver tube920. As the bracket 902 displaces the load sensor pins 8, 9 (the ends ofwhich are rigidly attached to the adapter 904), the sheer force causesthe magneto-elastically active portions 140 a, 140 b to output amagnetic field that is detectable by magnetic field sensors 914 a, 914b.

For example, assume a force is applied to the proximate end of thedrawbar 930 in the direction shown. In this embodiment, the forcetransmitted to the back load sensor pin 9 may be determined with respectto the adapters 904-2, 904-4. The output signals from the magnetic fieldsensors associated with the load sensor pin 9 may be received in asuitable algorithm, for example one that is embedded on a circuit boardhaving a suitable processor located inside the load sensor pin 9, or ina separate module 980 (FIG. 12A) that could be integrated into thetowing vehicle electronics. The received output signals from the loadsensor pin 9 (and from the load sensor pin 8) may be indicative of themagnetic field/flux exhibited by the load sensor pins, and thus may beused to determine that a force has vector components of 6653 N in thex-direction and −5138 N in the y-direction (associated with the x-y-zCartesian coordinate system shown). Moreover, the received outputsignals may be further used to determine that the other force vectorcomponents are −6245 N in the x-direction and 6 N in the y-direction asshown. The algorithm/processor may compute that the force applied to theproximate end of the drawbar 930 has a magnitude of 3514 N and isapplied in the direction shown (i.e., toward the right or in they-direction). The table below indicates the forces that may bedetermined as a result of forces transmitted to the load sensor pins 8,9.

TABLE 1 Force Vectors on Adapters Front Reaction (N) Joint Probe (N)Total (N) 904-1 x 5387.6 0 5387.6 y 6.3344 0 6.3344 z −2082.9 −1012.4−3095.3 904-3 x −5513.2 0 −5513.2 y 1641.7 −29.643 1612.057 z 4731.4−1772.6 2958.8 904-2 x 6652.6 0 6652.6 y −5018.3 −119.39 −5137.69 z399.02 −5634.6 −5235.58 904-4 x −6245.6 0 −6245.6 y 5.6106 0 5.6106 z2745.4 2626.7 5372.1

The information about the applied force at the proximate end of thedrawbar 930, and related information (such as a result of a comparisonof the force computation to a pre-determined force threshold or limitvalue), may be provided to the towing vehicle for any number of usefulpurposes, such as displaying the information and/or related informationto the vehicle operator or as input to a vehicle system such as abraking system, a stability system, a transmission system, a trailerbacking system, or an engine controller system.

Turning now to FIG. 18B, shown therein is another simplified, partial,perspective view diagram of some of the components of the tow couplingapparatus of FIG. 14 showing a different load case as summarized in thefollowing table.

TABLE 2 Force Vectors on Adapters Front Reaction (N) Joint Probe (N)Total (N) 904-1 x 9285.7 0 9285.7 y −3343 0 −3343 z −2947.5 −1493.6−4441.1 904-3 x −9282.6 0 −9282.6 y 5.0979 −65.01 −59.9121 z 5260.1−1087.9 4172.2 904-2 x 11322 0 11322 y 8.541 −128.91 −120.369 z 893.49−5098.8 −4205.31 904-4 x −10776 0 −10776 y 9.5836 0 9.5836 z 2265.82208.5 4474.3

Turning now to FIG. 19A, FIG. 19B, and FIG. 19C, shown therein aresimplified, partial, perspective view diagrams of the vehicle towcoupling apparatus of FIG. 14 in which a shielding device 190 is used tosurround the load sensor pins 8, 9 for shielding the magneto-elasticallyactive portions 140 a, 140 b and the magnetic field sensors 914 a, 914 bfrom external magnetic fields. The shielding device 190 is preferablymade from or utilizes highly magnetically permeable materials to conductexternal magnetic fields away from the load sensor pins 8, 9. Theshielding device 190 provides openings for sheathed cables 192, 194,which connect the electronics of the load sensor pins 8, 9 to externalcircuits, to pass through the shielding device 190. In case of an ACnear field source, even a thin metal shielding device 190 is able toprovide good shielding. An external AC magnetic field will create eddycurrents inside of the shield material, which in turn will create amagnetic field that opposes the incident field, thereby cancelling theincident field. The shielding material may be magnetic or non-magneticbut should have a high electric conductivity.

Turning now to FIG. 20, shown therein is a simplified, side view diagramof the tow coupling apparatus of FIG. 14 showing another load case. Inparticular, a drawbar 930 with a ball-style hitch (typically welded orbolted to the proximate or free end of the drawbar 930) is showninserted in the receiver tube 920 and held in place with a fastening pin(other devices for connecting the drawbar and receiver are alsocontemplated). The large arrows indicate the forces that might act onthe assembled tow coupling apparatus in the plane of the diagram (x-zplane, assuming the y-direction is out of the page).

An algorithm (such as in the form of embedded software in/on the loadsensor pins 8,9 or in the separate module 980 (FIG. 12A)) may utilizevalues for the following variables (all linear dimensions are measuredalong the x- or z-direction as shown):

TABLE 3 Variable/Parameter Type/Description Load sensor pin, outerdiameter Length (mm) Load sensor pin, inner diameter Length (mm) Loadsensor pin, width overall Length (L) (mm) Load sensor pin, height Length(h_(pins)) (mm) Drawbar drop Length (mm) Drawbar drop height Length(h_(drop) (mm)) Distance to back load sensor pin 9 Length (d_(A)) (mm)Distance between load sensor pins Length (d_(pins)) (mm) Drawbarfastening pin hole size, diameter Length (mm) Distance between the endof the drawbar and Length (mm) the drawbar fastening pin hole Distancebetween the coupling point (ball) Length (mm) and the drawbar fasteningpin hole Distance of the material between the two load Length (mm)sensor pins Distance from the back load sensor pin to the Length (mm)back end of the tow coupling apparatus Distance between the drawbarfastening pin Length (mm) hole and the front load sensor pin

Inputs associated with each of the above variables will be processed bythe aforementioned processor which executes software algorithms that areembedded in/on the memory or storage device on the printed circuitboards 304, 604 of the load sensor pins 8, 9, or that are embedded in/ona printed circuit board of the separate module 980 outside the loadsensor pins 8, 9. The inputs are used in at least the followingequations:

$\begin{matrix}{{\sum F_{L}} = {0\text{:}}} & (1) \\{{F_{L} - A_{L}} = 0} & (2) \\{{\sum F_{V}} = {0\text{:}}} & (3) \\{{F_{V} + A_{V} - B_{V}} = 0} & (4) \\{{\sum M_{A}} = 0} & (5) \\{{{B_{V} \cdot d_{Pins}} + {F_{V} \cdot d_{A}} + {F_{L} \cdot \left( {h_{Pins} + h_{Drop}} \right)}} = 0} & (6) \\{A_{L} = F_{L}} & (7) \\{A_{V} = {{- F_{V}} + B_{V}}} & (8) \\{B_{V} = \frac{{{- F_{V}} \cdot d_{A}} - {F_{L} \cdot \left( {h_{Pins} + h_{Drop}} \right)}}{d_{Pins}}} & (9)\end{matrix}$

In one embodiment, the software computes a tongue force (F-tongue), towforce (F-tow), and a sway force (F-sway) according to industry-specificand federal specifications, such as those of Ultimate Load (per SAE J684for Hitch Test Loads), and Ultimate Loads (per SAE J684 Strength TestLoads for Balls and Trailer couplings). Other methods and standards mayalso be used, including those for other countries/regions (e.g.,European Union).

In another embodiment, the embedded software may be used to receivesignals from various other sensors (not shown) and output a signalcontaining information useful in determining or assessing a load weightgauge (measuring the tongue load of a coupling between the tow andtowing vehicles), a tow load weight shift alert, an unsafe towed vehicleload distribution alert, a towing vehicle limit notification, anautomated towed vehicle brake control (closed loop) signal, a low/flattowed vehicle tire notification, a check towed vehicle brakenotification, a closed loop braking control, a towing vehicle shiftcontrol, a towing vehicle engine control, and a towing vehicle stabilitycontrol.

In still another embodiment, the software may provide a signalcorresponding to a value in a pre-determined output range (provided in,e.g., N and lb), an ultimate or maximum load weight carrying output(provided in, e.g., N and lb), and an ultimate or maximum ball load andtrailer hitch output (also in, e.g., N and lb).

Additional software inputs may include load sensor pin outer diameter,inner diameter, wall thickness, free length L, and sheer points (all inmillimeters). Calculated stress values may include maximum sheer stressand bending stress, among others (all in N/mm²). A static safety factormay also be computed.

Turning now to FIG. 21, shown therein is a simplified, side view diagramof a tow coupling apparatus and vehicle components. In particular, thetow coupling apparatus is mounted such that it does not interfere with abumper step 940 (which is above the hitch tube 922) and spare tire 944(which is behind the hitch tube 922, in some cases by only a few inches,such as 3 inches). Spare tires stored below a towing vehicle's bodyframe or other components are typically lowered to the ground by a cableand winch mechanisms (not shown), and can swing on the cable andpotentially strike the tow coupling apparatus. To ensure that the sparetire 944 avoids striking the tow coupling apparatus upon being raised orlowered, an angled guide member 942 is positioned forward of the towcoupling apparatus and between the tow coupling apparatus and the sparetire 944 as shown.

Turning now to FIG. 22 through FIG. 27, shown therein are simplified,schematic, exploded, perspective and plan view diagrams of another towcoupling apparatus for coupling a towing vehicle to a towed vehicle.FIG. 22 is a simplified, perspective view diagram of one component of atow coupling apparatus showing upper and lower load sensor pins 8, 9 foruse with a towed vehicle coupler 220, which mates with a towing vehiclecoupler 230. In the embodiments shown, the load sensor pins 8, 9 arearranged generally vertically (along z-axis) with respect to each other(as compared to, for example, the embodiments of FIG. 13 and FIG. 14, inwhich the load sensor pins 8, 9 are arranged horizontally (alongx-axis)). The two load sensor pins 8, 9 are positioned in the towedvehicle coupler 220 in respective upper and lower brackets 222-1, 222-2,with or without bushings. The towing vehicle coupler 230 includes fouradapters 232-1, 232-2, 232-3, 232-4 such that the through-holes on theupper bracket 222-1 are axially aligned with the through-holes of theadapters 232-1, 232-2, and the through-holes on the lower bracket 222-2are axially aligned with the through-holes of the adapters 232-3, 232-4.When aligned, the load sensor pins 8, 9 may be rigidly fixed in thethrough-holes, such that the couplers 220 and 230 may be coupledtogether as illustrated in FIG. 24.

In FIG. 25, the towed vehicle coupler 220 is modified such that itincludes a hitch part 220 a having a bracket 250 and through-holes 252,and a coupler part 220 b having through-holes 254. The through-holes252, 254 permit a user to vertically adjust (z-axis) the relativeposition of the hitch part 220 a and the coupler part 220 b with respectto each other (a fastening pin, not shown, is inserted into thethrough-holes 252, 254, once they are axially aligned). When the hitchpart 220 a, couplers part 220 b, and towing vehicle coupler 230 aligned,the load sensor pins 8, 9 may be rigidly fixed in the through-holes,such that the tow coupling apparatus may be coupled together asillustrated in FIG. 26.

Turning now to FIG. 27, shown therein is a simplified, process flowdiagram 270 describing a method for rigidly fixing the load sensor pins8, 9 inside the brackets and adapters as shown and described above. Asan initial step, the load sensor pins 8, 9 are first received along withthe various tow coupling apparatus components. With reference to FIG.13, for example, these would include providing a bracket 902 attached toa receiver tube 920, and a generally U-shaped adapter 904 attached to ahitch tube 922.

In a first treatment step 272, the first magneto-elastically activeregion 21 and the second magneto-elastically active region 22 of theload sensor pins 8, 9 are each directly or indirectly attached to orform respective parts of the load sensor pins 8, 9, such that the loadsensor pins 8, 9 will have the characteristics previously described (themagneto-elastic properties are described in more detail in theaforementioned Applicant's patents incorporated by reference).

In a second treatment step 274, when it is desired for the load sensorpins 8, 9 to have one or more collars (not shown) around all or aportion of the end portions 130 a, 130 b of the load sensor pins 8, 9,the collars are arranged such that the positions of the one or morecollars substantially correspond to one or more of the positions of thethrough-holes 924-1, 924-2 on the side wall 904 b of the bracket 904,and through-holes 924-3, 924-4 on the side wall 904 a of the bracket904. Also, when it is desired for the bracket 902 and adapter 904 to beconfigured in such a way as to provide a gap therebetween, a gapmaterial may be inserted.

In the next step 276, the load sensor pins 8, 9, and when necessary thecollars/bushing 906 a, 906 b, 906 c, 906 d, 908 a, 908 b, 908 c, 908 d(as best seen in FIG. 9), may be cryogenically treated to reduce theircross-section dimension to permit inserting in the respectivethrough-holes.

In the next step 278, respective printed circuit board 304, 604 withmagnetic field sensors are mounted or arranged proximate to themagneto-elastically active portion 140 a, 140 b either before or afterthe load sensor pins 8, 9 are treated and positioned in the respectivethrough-holes after being treated.

In a next step, the cryogenically treated load sensor pins 8, 9, and thevarious tow coupling apparatus components described above are allaligned. The load sensor pins 8, 9 are then inserted and the load sensorpins 8, 9 and other components are allowed to return to ambienttemperature. The cryogenic treatment process may be conducted inconjunction with (such as following) a heat treatment process performedon the load sensor pins 8, 9. Both treatment processes are performed ina manner such that crystalline changes following magnetization of theload sensor pins 8, 9 is avoided.

Turning now to FIG. 28A and FIG. 28B, shown therein are simplified,partial, exploded, perspective view diagrams of another type of vehicletow coupling apparatus 100 incorporating the load sensor pins 8, 9. Thetow coupling apparatus 100 includes a sensor assembly 1 for forcesensing. The sensor assembly includes a first portion 2 (supportingyoke) having a first through-hole 3 and a second through-hole 4, asecond portion 5 (receiving tube) having a third through-hole 6 andfourth through-hole 7. The third and fourth through-holes 6, 7 arepositioned in correspondence to the first and second through-holes 3, 4.

The second portion defines a Cartesian coordinate system having alongitudinal x-axis direction, a transversal y-axis direction, and avertical z-axis direction. The longitudinal direction extends in thedirection of longitudinal extension of the second portion. Thetransversal direction extends in a direction perpendicular to thelongitudinal direction and in a horizontal plane. The vertical directionextends in a direction that perpendicular to the longitudinal directionand the transversal direction.

The sensor assembly 1 further includes a first load sensor pin 8 and asecond load sensor pin 9. The load sensor pin 8 is arranged such that itextends through the first and third through-holes 3, 6. The load sensorpin 9 is arranged such that it extends through the second and fourththrough-holes 4, 7. The first portion 2 is coupled to the second portion5 via the first and second load sensor pins 8, 9.

At least one out of the first and the second load sensor pin 8, 9includes at least one magneto-elastically active region 10 (as shown inFIG. 30) that is directly or indirectly attached to or forms a part ofthe load sensor pin 8, 9 in such a manner that mechanic stress of theload sensor pin 8, 9 is transmitted to the magneto-elastically activeregion 10. The magneto-elastically active region 10 includes at leastone magnetically polarized region such that a polarization of thepolarized region becomes increasingly helically shaped as the appliedstress increases.

The at least one load sensor pin 8, 9 further includes a magnetic fieldsensor means arranged approximate the at least one magneto-elasticallyactive region 10 for outputting a signal corresponding to astress-induced magnetic flux emanating from the magnetically polarizedregion.

The magnetic field sensor means includes at least one directionsensitive magnetic field sensor L. The at least one direction sensitivemagnetic field sensor is configured for determination of a shear forcein at least one direction. The at least one direction sensitive magneticfield sensor L is in particular arranged to have a predetermined andfixed spatial coordination with the respective load sensor pin 8, 9.

The load sensor pin 8, 9 includes the at least one direction sensitivemagnetic field sensor L is at least partially hollow. The at least onedirection sensitive magnetic field sensor L is arranged inside theinterior of the pin 8, 9.

The first through-hole 3 and the third through-hole 6 are configuredsuch that they encompass the first load sensor pin 8 in apositive-fitting manner. In other words, the first load sensor pin 8extends through the first and third through-holes 3, 6, and the firstload sensor pin 8 is supported in at least two rotational degrees offreedom and at least two translational degrees of freedom by abuttingsurfaces of the through-holes.

The second load sensor pin 9 is encompassed by the second through-hole 4in a positive-fitted manner. In other words, the second load sensor pin9 extends through the second through-hole 4, and the second load sensorpin 9 is supported in at least two rotational degrees of freedom and atleast two translational degrees of freedom by abutting surfaces of thesecond through-hole 4.

The fourth through-hole 7 is configured such that the second load sensorpin 9 has one additional degree of freedom of movement (compared to thefirst load sensor pin 8 in the third through-hole 6) within the fourththrough-hole 7. Differently stated, the second load sensor pin 9 extendsthrough fourth through-hole 7, and the second load sensor pin 9 issupported in at least two rotational degrees of freedom and at least onetranslational degree of freedom by abutting surfaces of thethrough-holes. The number of translational degrees of freedom of thesecond load sensor pin 9 in the fourth through-hole 7 is one more thanthe number of translational degrees of freedom of the first load sensorpin 8 the third through-hole 6.

The additional degree of freedom is a translational degree of freedomthat extends in the longitudinal x-axis direction.

The first portion 2 has a yoke-like shape, wherein yoke legs 11 of thefirst portion comprise the first through-hole 3 and second through-hole4. The second portion 5 has a tubular shape, wherein side walls and/or acenter wall of the second portion 5 comprise the third through-hole 6and the fourth through-hole 7.

The direction sensitive magnetic field sensor is (or the directionsensitive magnetic field sensors are) configured to detect forcecomponents of shear forces introduced into the load sensor pins 8, 9 bythe first portion 2 and the second portion 5.

The first and/or second load sensor pin 8, 9 is fixedly attached (in allsix degrees of freedom in a predetermined manner to the first portion 2.Bolts 12 screw the load sensor pins 8, 9 (via attachment flanges of thepins) to yoke legs 11 of the first portion 2.

The second portion 5 includes a center wall 13 extending in thelongitudinal x-axis direction and the vertical z-axis direction, thethird through-hole 6 and fourth through-hole 7 extend through the centerwall 13 (as best seen in FIG. 29).

The first portion 2 has a yoke-like shape, wherein the yoke legs 11 ofthe first portion 2 comprise the first and second through-holes 3, 4,and wherein the center wall includes the third and fourth through-holes6, 7.

Direction sensitive magnetic field sensor(s) L is/are configured todetect force components of shear forces introduced into the load sensorpins 8, 9 by the first portion 2 and the second portion 5.

Side walls 14 of the second portion 5 comprise through-holes in sidewalls that are larger than the third and fourth through-holes 6, 7, suchthat the shear forces are introduced into the load sensor pins 8, 9 byabutment surfaces of the first and second through-holes 3, 4 in the yokelegs 11 and abutment surfaces of the third and fourth through-holes 6, 7in the center wall 13.

The tow coupling apparatus 100 includes the sensor assembly 1. The firstportion 2 is a tow coupling apparatus that is attached to a hitch tube101 of a towing vehicle.

The second portion 5 is a receiving tube that is configured to receive adrawbar 102 (hitch bar, ball mount) of the tow coupling apparatus 100.The drawbar 102 can be partially inserted into the second portion 5. Apin 103 secures the drawbar 102 to the second portion 5.

Turning now to FIG. 30, shown therein is a simplified, cross-sectionalview diagram of another tow hitch sensor assembly including first andsecond load sensor pins 8, 9 extend through the first through-hole 3 andthe second through-hole 4 in the first portion 2 and through the thirdthrough-hole 6 and the fourth through-hole 7 in the second portion 5.The first and/or second load sensor pins 8, 9 is an at least partiallyhollow pin that may be sealed by a front cover 15 and a rear cover 16.The rear cover 16 may provide a cable bushing to provide access forsupply and/or signal lines 17. The load sensor pins 8, 9 include aplurality of direction sensitive field sensors L. A printed circuitboard 18 supports the direction sensitive field sensors L. The loadsensor pins 8, 9 can include one or more collars 19 of comparatively lowmagnetic permeability (compared to the hollow shaft of the load sensorpins 8, 9) arranged such that the positions of the one or more collars19 substantially correspond to one or more of the positions of thethrough-holes 3, 4, 6, 7 in the first and/or second portion.Alternatively, one or more of the through-holes 3, 4, 6, 7 can comprisea collar/bushing 19 of comparatively low magnetic permeability (comparedto the hollow shaft of the load sensor pins 8, 9). The first portion 2and the second portion 5 may be configured to provide a gap between thefirst portion 2 and the second portion 5. The gap may comprise amaterial of low magnetic permeability (compared to the hollow shaft ofthe load sensor pins 8, 9).

Turning now to FIG. 31A and FIG. 31B, shown therein are a simplified,partial, cross-sectional plan and end view diagrams of anotherconfiguration of the load sensor pins 8, 9 as used in, for example, thetow coupling apparatus of FIG. 30. The first and/or the second loadsensor pin 8, 9 includes at least one respective first x-axis directionsensitive magnetic field sensor Lx11, Lx12 configured to detect a forcecomponent Fx1 in the first magneto-elastically active region 21 in thelongitudinal x-axis direction. The first and/or the second load sensorpins 8, 9 includes at least one respective second x-axis directionsensitive magnetic field sensor Lx21, Lx22 configured to detect a forcecomponent Fx2 in the second magneto-elastically active region 22 in thelongitudinal x-axis direction. The first and/or the second load sensorpins 8, 9 includes at least one respective first z-axis directionsensitive magnetic field sensor Lz11, Lz12 configured to detect a forcecomponent Fz1 in the first magneto-elastically active region 21 in thevertical x-axis direction. The first and/or the second load sensor pins8, 9 includes at least one second z-axis direction sensitive magneticfield sensor Lz21, Lz22 configured to detect a force component Fz2 inthe second magneto-elastically active region in the vertical z-axisdirection.

The sensor means includes at least four magnetic field sensors L havinga first to fourth sensing direction, wherein the sensing directions anda shaft axis A (FIGS. 32A and 32B) are at least substantially parallelto each other. The first to fourth magnetic field sensors are arrangedalong the circumference of the load sensor pin 8, 9 having substantiallyequal distances in circumferential direction between each other.

The at least one magneto-elastically active regions 21, 22 project alonga circumference of the respective load sensing pin 8, 9, wherein theregions are magnetized in such a way that the domain magnetizations inthe magnetically polarized regions 21, 22 are in a circumferentialdirection of the member.

Turning now to FIG. 32A and FIG. 32B, shown therein are simplified,partial, axial, cross-sectional view diagrams of a load sensor pin 8, 9for use in a tow coupling apparatus, in which a sensor assembly 1 has afirst portion 2 coupled to a second portion 5 via the load sensor pins8, 9. The first portion 2, which may correspond to the adapter 904, issubject to a first shear force FS1 pointing to the left. The secondportion 5, which may correspond to the bracket 902, is exposed to asecond and opposite shear force FS2, pointing to the right. The loadsensor pin 8, 9 includes a magneto-elastically active region 21, whichis arranged at the transition between the first and the second portion2, 5. Consequently, the active region 21 is subject to shear forcescausing the magnetic flux emanating from the magnetically polarizedregion of said active region 21 to become increasingly helically shaped,when the shear forces FS1, FS2 increase. The sensor means of the loadsensor pins 8, 9 includes four direction sensitive magnetic fieldsensors Lx1, Lx2, Lz1, Lz2 being arranged along the inner circumferenceof the load sensor pin 8, 9.

The first direction sensitive sensor Lx1 and the third directionsensitive sensor Lx2 form a first group of magnetic field sensors.

The second group of sensors consists of the second direction sensitivesensor Lz1 and the fourth direction sensitive sensor Lz2.

The sensing direction Sx1 of the first sensor Lx1 is 180 degreesopposite to the third sensing direction Sx2 of the third sensor Lx2.

The first sensing direction Sx1 points out of the paper plane, the thirdsensing direction Sx2 points into the paper plane.

Similar to the first group of sensors Lx1, Lx2, the second sensingdirection Sz1 and the fourth sensing direction Sz2 are 180 degreesopposite to each other.

The second and fourth sensor Lz1, Lz2 are arranged accordingly.

As it is indicated using the commonly known direction signs, the secondsensing direction Sz1 points out of the paper plane while the fourthsensing direction Sz2 is directed into the paper plane.

The second sensor Lz1 (having the second sensing direction Sz1) and thefourth sensor Lz2 (having the fourth sensing direction Sz2) are shown.

The first sensor Lx1 and the first sensing direction Sx1 are shownsolely for clarification of the configuration of the sensors. Naturally,the first sensor Lx1 is not arranged in a common plane with the secondand fourth sensor Sz1, Sz2.

FIG. 32B shows a simplified cross section of a load sensor pin 10according to another embodiment, which includes a first or upper member11, which is coupled to a second or lower member 12 via the shaft likemember 4. The upper member 11 is subject to a first shear force FS1pointing to the left. The lower member 12 is exposed to a second andopposite shear force FS2, pointing to the right. The shaft like member 4includes an active region 6, which is arranged at the transition betweenthe upper and lower member 11, 12. Consequently, the active region 6 issubject to shear forces causing the magnetic flux emanating from themagnetically polarized region of said active region 6 to becomeincreasingly helically shaped, when the shear forces FS1, FS2 increase.The sensor means of the load sensor pin 10 includes four directionsensitive magnetic field sensors LX1, LX2, LY1, LY2 being arranged alongthe inner circumference of the shaft like member 4.

Turning now to FIG. 33, shown therein is a simplified, cross-sectionalview diagram of some of the components of a tow coupling apparatus inwhich the first portion 2 surrounds the second portion 5, which isexposed to a force F. The load sensor pin 8, 9 intersects the first andthe second portions 2, 5 along the shaft axis A. The load sensor pin 8,9 includes a first magneto-elastically active region 261 and a secondmagneto-elastically active region 262. Similar to the other embodimentsof the invention, these regions are directly or indirectly attached toor form a part of the load sensor pin 8, 9 in such a manner that themechanic stress is transmitted to the active regions 261, 262. Theactive regions 261, 262 are magnetically polarized in oppositecircumferential directions, P61, P62, which are substantially 180degrees opposite to each other. Furthermore, the directions ofpolarizations are substantially perpendicular to the shaft axis A.

A first pair of magnetic field sensors comprising a first sensor L1 anda second sensor L2 arranged inside the load sensor pin 8, 9 in that thispair of sensors cooperates with the first active region 261. Similar, asecond pair of magnetic field sensors comprising a first and a secondsensor L1* and L2* arranged inside the load sensor pin 8, 9 so as tointeract with the second active region 262. The sensors L1, L2 of thefirst pair and the sensors L1*, L2* of the second pair are arrangedapproximate the first and the second magneto-elastically active region261, 262, respectively. The first sensor pair L1, L2 outputs a firstsignal S, which is illustrated as a voltage V varying with the appliedforce F in the lower left of FIG. 33. The signal S corresponds to astress-induced magnetic flux emanating from the first magneticallypolarized region 261.

Similarly, the second pair of magnetic sensors L1*, L2* outputs a secondsignal S* corresponding to a stress-induced magnetic flux emanating fromthe second magnetically polarized region 262. This signal S* is also avoltage V* varying with the applied F (see lower right of FIG. 33).However, the slope of the second signal S* is opposite to that of thefirst signal S. A control unit (not shown) of the magneto-elastic sensorassembly is configured for determination of the force F inducing astress in the load sensor pin 8, 9. The control unit performs adifferential evaluation of the signals S and S* of the first pair ofsensors L1, L2 and the second pair of sensors L1*, L2*. Thisdifferential evaluation advantageously doubles the sensitivity of thesignal, which is correlated with the applied stress. Because thepolarization P61 and P62 of the first and second magnetically activeregion 261, 262 is opposite to each other, theoretically possibleexternal fields are compensated. The magneto-elastic sensor assemblyaccording to this embodiment is more sensitive and less susceptible toerrors.

Advantageously, all embodiments of the invention may be equipped withthe sensor configuration of FIG. 33 having separate, oppositelypolarized active regions 261, 262 and two corresponding sets i.e. pairsof sensors L1, L2 and L1*, L2*.

Furthermore, the embodiment of FIG. 8 may be equipped with the sensorconfiguration, which is known from the load pin in FIG. 31B. In otherwords, the sensor pairs L1, L2 and L1*, L2* may be replaced by a sensorconfiguration having four sensor pairs Lx11/Lx12, Lx21/Lx22, Lz11/Lz12,Lz21/Lz22. According to this particular embodiment of the invention,additional force vectors may be determined.

Turning now to FIG. 34, shown therein is a simplified, side, plan viewdiagram of a portion of the vehicle tow coupling apparatus of FIGS. 28Aand 28B showing a first simplified load case. In particular, showntherein are the forces associated with the simplified load case. A forceF has a vertical force component Fz in the vertical z-axis direction.The force F is applied to the sensor assembly via the second portion 5,and more precisely via the ball coupling 104 of the drawbar 102. Fordetermining the force component Fz the following set of equations aresolved:

Fz*d1=Fz1*d2  (10)

Fz*d3=Fz2*d2  (11)

Fz=Fz1+Fz2  (12)

d1=Fz1*d2/(Fz1+Fz2)  (13)

d3=Fz2*d2/(Fz1+Fz2)  (14)

Fz1 is a reaction force on the first load sensor pin 8, Fz2 is areaction force on the second load sensor pin 9. Distance d2 is thedistance between (the axes of) the first and the second load sensor pins8, 9. Distance d1 is the distance between the point of load (the ballcoupling 104) and (the axis of) the second load sensor pin 9. Distanced3 is the distance between the point of load and (the axis of) the firstload sensor pin 8. An algorithm for solving the above equations may beembedded in/on the memory of one of the aforementioned printed circuitboard 304, 604.

Turning now to FIG. 35, shown therein is a simplified, top view diagramof a portion of a vehicle tow coupling apparatus showing anothersimplified load case. The force has a transversal force component Fy inthe transversal y-axis direction applied to the sensor assembly 1 viathe second portion 5, and more precisely via the ball coupling 104 ofthe drawbar 102. The fourth through-hole 7 provides a degree of freedomin the longitudinal x-axis direction. The transversal force component Fycreates a first reactive force Fx2 acting in the longitudinal x-axisdirection on the first magneto-elastically active region 21 of the firstload sensor pin 8, and a second reactive force Fx1 acting in thelongitudinal x-axis direction on the second magneto-elastically activeregion 22 of the first load sensor pin 8. For determining the forcecomponent Fy, the following set of equations are solved:

Fy*d3=Fx1*d2  (15)

Fy*d3=Fx2*d2  (16)

Fx1=−Fx2  (17)

Turning now to FIG. 36, shown therein is a simplified, top view diagramof a portion of a vehicle tow coupling apparatus showing anothersimplified load case. In this case, the force has a longitudinal forcecomponent Fx in the longitudinal x-axis direction applied to the to thesensor assembly 1 via the second portion 5, and more precisely via theball coupling 104 of the drawbar 102. The fourth through-hole 7 providesa degree of freedom in the longitudinal x-axis direction. Thelongitudinal force component Fx creates a first reactive force F2 actingin the longitudinal x-axis direction on the first magneto-elasticallyactive region 21 of the first load sensor pin 8, and a second reactiveforce F1 acting in the longitudinal x-axis direction on the secondmagneto-elastically active region 22 of the first load sensor pin 8. Fordetermining the force component Fx, the following equation is solved:

Fx=Fx1+Fx2  (18)

Turning now to FIG. 37, shown therein is a simplified, cross-sectionalend view and plan side view diagram of a vehicle tow coupling apparatussubject to a vertical load component, Fz of a load F. The first loadsensor pin 8 includes a first magneto-elastically active region 21 and asecond magneto-elastically active region 22 (as shown in FIG. 36) thatare directly or indirectly attached to or form parts of the first loadsensor pin 8 in such a manner that mechanic stress that is applied tothe first load sensor pin 8 is transmitted to the magneto-elasticallyactive regions 21, 22. Each magneto-elastically active region 21, 22includes a magnetically polarized region. The magnetic polarization ofthe first magneto-elastically active region 21 and the magneticpolarization of the second magneto-elastically active region 22 can besubstantially opposite to each other.

A magnetic field sensor means includes at least one first directionsensitive magnetic field sensor Lz11 being arranged approximate thefirst magneto-elastically active region for outputting a first signalcorresponding to a stress-induced magnetic flux emanating from the firstmagnetically polarized region 21, and at least one second directionsensitive magnetic field sensor Lz21 being arranged approximate thesecond magneto-elastically active region 22 for outputting a secondsignal corresponding to a stress-induced magnetic flux emanating fromthe second magnetically polarized region 22.

The first load sensor pin 8 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a force component Fz1 in the firstmagneto-elastically active region 21 in the vertical z-axis direction;and

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a force component Fz2 in thesecond magneto-elastically active region in the vertical z-axisdirection.

The second load sensor pin 9 is a naked pin, i.e. the pin has nomagneto-elastically active region and no direction sensitive magneticfield sensors. Differently stated, the first load sensor pin 8 includesat least one first z-axis direction sensitive magnetic field sensor Lz11and at least one second z-axis direction sensitive magnetic field sensorLz21.

The first and second load sensor pins 8, 9 are rigidly fixed within thefirst and second through-holes 3, 4 of the first portion 2 (as shown inFIG. 36). The third and the fourth through-holes 6, 7 can provide aminimal gap between the abutment surfaces of the second portion 5 andthe first and second load sensor pins 8, 9.

Turning now to FIG. 38, shown therein is a simplified, cross-sectionalend view and plan side view diagram of a vehicle tow coupling apparatussubject to a vertical, transversal, and longitudinal load components ofa load F. In this view, a first load sensor pin 8 includes a firstmagneto-elastically active region 21 and a second magneto-elasticallyactive region 22, which are directly or indirectly attached to or formparts of the first load sensor pin 8 in such a manner that mechanicstress that is applied to the first load sensor pin 8 is transmitted tothe magneto-elastically active regions 21, 22. Each magneto-elasticallyactive region 21, 22 includes a magnetically polarized region. Themagnetic polarization of the first magneto-elastically active region 21and the magnetic polarization of the second magneto-elastically activeregion 22 can be substantially opposite to each other.

A magnetic field sensor means includes at least one first and thirddirection sensitive magnetic field sensor Lx11, Lz11 being arrangedapproximate the first magneto-elastically active region for outputting afirst signal and a third signal corresponding to a stress-inducedmagnetic flux emanating from the first magnetically polarized region 21.The magnetic sensor means further includes at least one second andfourth direction sensitive magnetic field sensor Lx21, Lz21 beingarranged approximate the second magneto-elastically active region 22 foroutputting a second signal and a fourth signal corresponding to astress-induced magnetic flux emanating from the second magneticallypolarized region 22.

The first load sensor pin 8 may include:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz11 in thefirst magneto-elastically active region 21 in the z-axis verticaldirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz12in the second magneto-elastically active region in the z-axis verticaldirection;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, Lx12 configured to detect a longitudinal force component Fx2 inthe first magneto-elastically active region 21 in the longitudinalx-axis direction; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx1 in the second magneto-elastically active region in the longitudinalx-axis direction.

The second load sensor pin 9 may include:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz21 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection; and

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz22in the second magneto-elastically active region in the vertical z-axisdirection;

Differently stated, the first load sensor pin 8 includes at least onefirst x-axis direction sensitive magnetic field sensor Lx11, at leastone second x-axis direction sensitive magnetic field sensor Lx21, atleast one first z-axis direction sensitive magnetic field sensor Lz11,and the at least one second z-axis direction sensitive magnetic fieldsensor Lz21. The second load sensor pin 9 includes at least one firstz-axis direction sensitive magnetic field sensor Lz11 and at least onesecond z-axis direction sensitive magnetic field sensor Lz21.

As previously described, the first and second load sensor pins 8, 9 arerigidly fixed within the first and second through-holes 3, 4 of thefirst portion 2. The third and the fourth through-holes 6, 7 can providea minimal gap between the abutment surfaces of the second portion 5 andthe first and second load sensor pins 8, 9.

Turning now to FIG. 39, shown therein is another simplified,cross-sectional end view and plan side view diagram of a vehicle towcoupling apparatus subject to a vertical, transversal, and longitudinalload components of a load F. In this view, a first load sensor pin 8includes a first magneto-elastically active region 21 and a secondmagneto-elastically active region 22, which are directly or indirectlyattached to or form parts of the first load sensor pin 8 in such amanner that mechanic stress that is applied to the first load sensor pin8 is transmitted to the magneto-elastically active regions 21, 22. Eachmagneto-elastically active region 21, 22 includes a magneticallypolarized region. The magnetic polarization of the firstmagneto-elastically active region 21 and the magnetic polarization ofthe second magneto-elastically active region 22 can be substantiallyopposite to each other.

The magnetic field sensor means of this embodiment includes at least onefirst and third direction sensitive magnetic field sensor Lx11, Lz11being arranged approximate the first magneto-elastically active regionfor outputting a first signal and a third signal corresponding to astress-induced magnetic flux emanating from the first magneticallypolarized region 21. The magnetic sensor means further includes at leastone second and fourth direction sensitive magnetic field sensor Lx21,Lz21 being arranged approximate the second magneto-elastically activeregion 22 for outputting a second signal and a fourth signalcorresponding to a stress-induced magnetic flux emanating from thesecond magnetically polarized region 22.

The first load sensor pin 8 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz11 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz12in the second magneto-elastically active region in the vertical z-axisdirection;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, L12 configured to detect a longitudinal force component Fx2 in thefirst magneto-elastically active region 21 in the longitudinal x-axisdirection; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx1 in the second magneto-elastically active region in the longitudinalx-axis direction.

The second load sensor pin 9 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz21 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz22in the second magneto-elastically active region 22 in the verticalz-axis direction;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, L12 configured to detect a longitudinal force component Fx10(force exerted by the load sensor pin 9 in contact with a top surface ofthe through-hole) in the first magneto-elastically active region 21 inthe longitudinal x-axis direction; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx20 (force exerted by the load sensor pin 9 in contact with a topsurface of the through-hole) in the second magneto-elastically activeregion 22 in the longitudinal x-axis direction.

Therefore, the configuration of the second load sensor pin 9 issubstantially similar to the configuration of the first load sensor pin8. Differently stated, the first load sensor pin 8 includes at least onefirst x-axis direction sensitive magnetic field sensor Lx11, at leastone the second x-axis direction sensitive magnetic field sensor Lx21, atleast one first z-axis direction magnetic field sensor Lz11, and atleast one second z-axis direction magnetic field sensor Lz21. The secondload sensor pin includes at least one first x-axis direction sensitivemagnetic field sensor Lx11, at least one second x-axis directionsensitive magnetic field sensor Lx21, at least one first z-axisdirection magnetic field sensor Lz11, and at least one second z-axisdirection magnetic field sensor Lz21.

The first and the second longitudinal force components Fx10, Fx20 arecomparatively small (for example, resulting from friction between theabutment surface of the fourth through-hole 7 and the second load sensorpin 9) or substantially zero. This is a direct result of the additionaltranslational degree of freedom in the longitudinal x-axis direction,which degree of freedom is provided by the fourth through-hole 7 in thesecond portion 5.

The first and second load sensor pins 8, 9 are rigidly fixed within thefirst and second through-holes 3, 4 of the first portion 2. The thirdand the fourth through-holes 6, 7 can provide a minimal gap between theabutment surfaces of the second portion 5 and the first and second loadsensor pins 8, 9.

Turning now to FIG. 40, shown therein is a simplified, cross-sectionalend view and plan side view diagram of a vehicle tow coupling apparatussubject to a vertical, transversal, and longitudinal load components ofa load F. In this view, the first load sensor pin 8 includes a firstmagneto-elastically active region 21 and a second magneto-elasticallyactive region 22, which are directly or indirectly attached to or formparts of the first load sensor pin 8 in such a manner that mechanicstress that is applied to the first load sensor pin 8 is transmitted tothe magneto-elastically active regions 21, 22. Each magneto-elasticallyactive region 21, 22 includes a magnetically polarized region. Themagnetic polarization of the first magneto-elastically active region 21and the magnetic polarization of the second magneto-elastically activeregion 22 can be substantially opposite to each other.

A magnetic field sensor means includes at least one first- andthird-direction sensitive magnetic field sensor Lx11, Lz11 beingarranged approximate the first magneto-elastically active region 21 foroutputting a first signal and a third signal corresponding to astress-induced magnetic flux emanating from the first magneticallypolarized region 21. The magnetic sensor means further includes at leastone second- and fourth-direction sensitive magnetic field sensor Lx21,Lz21 being arranged approximate the second magneto-elastically activeregion 22 for outputting a second signal and a fourth signalcorresponding to a stress-induced magnetic flux emanating from thesecond magnetically polarized region 22.

The first load sensor pin 8 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz11 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz12in the second magneto-elastically active region in the vertical z-axisdirection;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, L12 configured to detect a longitudinal force component Fx2 in thefirst magneto-elastically active region 21 in the longitudinal x-axisdirection; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx1 in the second magneto-elastically active region in the longitudinalx-axis direction.

The second load sensor pin 9 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz21 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz22in the second magneto-elastically active region 22 in the verticalz-axis direction;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, L12 configured to detect a longitudinal force component Fx22 inthe first magneto-elastically active region 21 in the longitudinalx-axis direction; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx21 in the second magneto-elastically active region 22 in thelongitudinal x-axis direction.

The general configuration of the second load sensor pin 9 issubstantially similar to the configuration of the first load sensor pin8. The first and second load sensor pins 8, 9 are rigidly fixed withinthe first and second through-holes 3, 4 of the first portion 2. Thethird and the fourth through-holes 6, 7 can provide a minimal gapbetween the abutment surfaces of the second portion 5 and the first andsecond load sensor pins 8, 9. Optionally, the fourth through-hole 7 canprovide no minimal gap, such that the second load sensor pin 9 isrigidly fixed within the third and the fourth through-hole 7.

Turning now to FIG. 41, shown therein is another a simplified,cross-sectional end view and plan side view diagram of a vehicle towcoupling apparatus subject to a vertical, transversal, and longitudinalload components of a load F. In this view, the first load sensor pin 8comprises a first magneto-elastically active region 21 and a secondmagneto-elastically active region 22, which are directly or indirectlyattached to or form parts of the first load sensor pin 8 in such amanner that mechanic stress that is applied to the first load sensor pin8 is transmitted to the magneto-elastically active regions 21, 22. Eachmagneto-elastically active region 21, 22 comprises a magneticallypolarized region. The magnetic polarization of the firstmagneto-elastically active region 21 and the magnetic polarization ofthe second magneto-elastically active region 22 can be substantiallyopposite to each other.

A magnetic field sensor means includes at least one first directionsensitive magnetic field sensor Lz11 being arranged approximate thefirst magneto-elastically active region for outputting a first signalcorresponding to a stress-induced magnetic flux emanating from the firstmagnetically polarized region 21. The magnetic sensor means furtherincludes at least one second direction sensitive magnetic field sensorLz21 being arranged approximate the second magneto-elastically activeregion 22 for outputting a second signal and a fourth signalcorresponding to a stress-induced magnetic flux emanating from thesecond magnetically polarized region 22.

The first load sensor pin 8 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz11 in thefirst magneto-elastically active region 21 of the first load sensor pin8 in the vertical z-axis direction; and

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz12in the second magneto-elastically active region of the first load sensorpin 8 in the vertical z-axis direction.

The first load sensor pin 8 comprises no x-axis direction sensitivemagnetic field sensors.

The second load sensor pin 9 includes:

a) a first and a third z-axis direction sensitive magnetic field sensorLz11, Lz12 configured to detect a vertical force component Fz21 in thefirst magneto-elastically active region 21 in the vertical z-axisdirection;

b) a second and a fourth z-axis direction sensitive magnetic fieldsensor Lz21, Lz22 configured to detect a vertical force component Fz22in the second magneto-elastically active region 22 in the verticalz-axis direction;

c) a first and a third x-axis direction sensitive magnetic field sensorLx11, Lx12 configured to detect a longitudinal force component Fx22 inthe first magneto-elastically active region 21 in the longitudinalx-axis direction; and

d) a second and a fourth x-axis direction sensitive magnetic fieldsensor Lx21, Lx22 configured to detect a longitudinal force componentFx21 in the second magneto-elastically active region 22 in thelongitudinal x-axis direction.

The first and second load sensor pins 8, 9 are rigidly fixed within thefirst and second through-holes 3, 4 of the first portion 2. The thirdand the fourth through-hole 6, 7 can provide a minimal gap between theabutment surfaces of the second portion 5 and the first and second loadsensor pins 8, 9. Optionally, the fourth through-hole 7 can provide nominimal gap, such that the second load sensor pin 9 is rigidly fixedwithin the third and the fourth through-hole 7.

Turning now to FIG. 42A, shown therein is a simplified, perspective,schematic view diagram of tow coupling apparatus 100 using load sensorpins 8, 9 for sensing (components) of a force F. In the configurationshown, the sensor assembly 1 for sensing a force F includes a firstportion 2 (attachment assembly, supporting yoke) having a first and asecond through-hole 3, 4, and a second portion 5 (trailer hitch, towinghook) having a third and fourth through-hole 6, 7. The third and fourththrough-holes 6, 7 are positioned in correspondence to the first andsecond through-holes 3, 4.

The sensor assembly 1 further includes a first load sensor pin 8 and asecond load sensor pin 9. The first load sensor pin 8 is arranged suchthat it extends through the first and third through-holes 3, 6. Thesecond load sensor pin 9 is arranged such that it extends through thesecond and fourth through-holes 4, 7.

The first portion 2 is coupled to the second portion 5 via the first andsecond load sensor pins 8, 9. At least one out of the first and thesecond load sensor pin 8, 9 includes at least one magneto-elasticallyactive region 10 that is directly or indirectly attached to or forms apart of the load sensor pin 8, 9 in such a manner that mechanic stresson the load sensor pin is transmitted to the magneto-elastically activeregion. The magneto-elastically active region 10 comprises at least onemagnetically polarized region such that a polarization of the polarizedregion becomes increasingly helically shaped as the applied stressincreases.

The at least one load sensor pin 8, 9 further includes a magnetic fieldsensor means arranged approximate the at least one magneto-elasticallyactive region 10 for outputting a signal corresponding to astress-induced magnetic flux emanating from the magnetically polarizedregion. The magnetic field sensor means includes at least one directionsensitive magnetic field sensor L, which is configured for determinationof a shear force in at least one direction. The at least one directionsensitive magnetic field sensor L is arranged to have a predeterminedand fixed spatial coordination with the load sensor pin 8, 9.

The load sensor pin 8, 9 comprising the at least one direction sensitivemagnetic field sensor L is at least partially hollow. The at least onedirection sensitive magnetic field sensor L is arranged inside theinterior of the load sensor pin 8, 9.

The first and second load sensor pins 8, 9 are substantially arrangedalong the vertical z-axis direction. The load sensor pins 8, 9 extend inthe transversal y-axis direction. The longitudinal direction isperpendicular to the vertical z-axis direction and the transversaly-axis direction to define the Cartesian coordinate system. The systemof equations that has to be solved in order to determine the respectiveload components of F, has to be altered accordingly.

Further features and aspects of the invention (which have been describedwith respect to the preceding embodiments) may also apply to thisembodiment.

The sensor assembly 1 is part of a tow coupling apparatus 100. The firstpart 2 is configured to be attached to the chassis of a towing vehicle.The second part 5 provides a ball coupling 104 that is configured tocouple to a towed vehicle.

Turning now to FIG. 42B and FIG. 42C, shown therein are simplified,perspective, schematic view diagrams of tow coupling apparatus 100 usingload sensor pins 8, 9 for sensing (components) of a force F. In theseembodiments, the load sensor pins 8, 9, along with the first part 2 andsecond part 5 (not shown), are integrated into the existing hitchmechanism with the load sensor pins 8, 9 arrange in the transversey-axis direction (perpendicular to the force F acting in the x-axisdirection).

Turning now to FIG. 42D through FIG. 42K, shown therein are simplified,perspective, schematic view diagrams of tow coupling apparatus 100 usingload sensor pins 8, 9 for sensing (components) of a force F. In theseembodiments, the load sensor pins 8, 9, along with the first part 2 andsecond part 5 (not shown), are integrated into the existing hitchmechanism with the load sensor pins 8, 9 arrange in the transversey-axis direction as shown (perpendicular to the force F acting in thex-axis direction). In some cases, an exterior housing further protectsthe components of the tow coupling apparatus 100 from rain, snow, ice,and other environment conditions.

Turning now to FIG. 42L and FIG. 420, shown therein is a simplified,perspective, schematic view diagram of tow coupling apparatus 100 usingload sensor pins 8, 9 for sensing (components) of a force F. In theseembodiments, the load sensor pins 8, 9, along with the first part 2 andsecond part 5 (not shown), are integrated into the existing hitchmechanism with the load sensor pins 8, 9 arrange in the longitudinalx-axis direction as shown (parallel to the force F acting in the x-axisdirection). Other load sensing pins 8, 9 could be positioned in thetransverse direction to better measure the Fx force in the x-axisdirection.

Turning now to FIG. 42P, shown therein is a simplified, perspective,schematic view diagram of coupling devices (“kingpin,” extender, 3-inchball, high-rise ball, inverted ball, and eyelet for use with agooseneck-style trailer hitch (not shown), and fifth wheel-style hitch)adapted to using one or more load sensor pins 8, 9 for sensing(components) of a force F acting on the coupling devices. FIG. 42Qthrough FIG. 42U show one of the coupling devices of FIG. 42P and thelocations for positioning the load sensor pins 8, 9 (usually in thetransverse direction) for sensing (components) of a force F acting onthe coupling devices. As shown, the coupling devices may include a hitchtube (which may be a solid bar) attached to a towing vehicle, a receivertube attached to the hitch tube/bar, a drawbar (which may be straight,curved) inserted in the receiver tube or attached directly to the hitchtube/bar, and a ball hitch.

Turning now to FIG. 42V, shown therein is a simplified, exploded,schematic view diagram of a weight sensor assembly 410 using load sensorpins 8, 9 for sensing a weight of a towed and a towing vehicle forcomparison to a predetermined value, such as a manufacturer's maximumweight limit or a US governmental gross vehicle weight rating (GVWR). A“sprung weight” is the weight of a mass resting on the suspension of avehicle or a trailer, not the total weight (the total weight wouldinclude the wheels, tires, brakes, and certain suspension components).As shown in the figure, the load sensor pins 8, 9 are positioned suchthat the sheer force exerted downward by the connection device 412(which could be a chassis or vehicle body part) and transferred to thevehicle wheels causes a force to be applied to the load pins 8, 9. Thebracket 902, which may be connected to the spring or other suspensioncomponent on the one end, and adapters 904, which may be attached to theconnection device 412 and the towing or the towed vehicle chassis, maybe used to output a signal (as described above) that approximates thesprung weight by measuring the force of the mass of the vehicle as itsweight force is transferred to the load sensor pins 8, 9. For example,the sensor assembly 410 could be positioned between the top of each ofthe four suspension springs associated with the wheels where the springsattach to the vehicle chassis.

FIGS. 42W through 42AA show various towed vehicles and towing vehiclesand related components, including suspension components, equipped withthe weight sensor assembly 410 at various measurement points between avehicle body or vehicle load (e.g., trailer box, boat) and the vehicle'swheels to measure a sprung weight force.

FIG. 42W for example, illustrates use of the weight sensor assembly 410positioned near a trailer wheel such that the weight sensor assembly 410is between the trailer box on one end and the wheel axel (or wheelsuspension component attached to the wheel), such that the weight of thetrailer box may be measured from a force arising from the weight of thetrailer box being transferred to the load sensor pins 8, 9. FIG. 42Xillustrates a similar use of the weight sensor assembly 410 on a smallertrailer.

FIG. 42Y illustrates use of the weight sensor assembly 410 positionednear a trailer wheel of a boat trailer such that the weight sensorassembly 410 is between the trailer on one end and the wheel axel (orwheel suspension component attached to the wheel), such that the weightof the boat and boat trailer may be measured from a force arising fromthe weight of the boat and boat trailer being transferred to the loadsensor pins 8, 9.

FIG. 42Z illustrates use of the weight sensor assembly 410 positionednear the three connection points of a leaf spring of a vehicle such thata weight sensor assembly 410 is between each of the two ends of the leafspring and the vehicle body above, and another weight sensor assembly410 is between the middle of the leaf spring and the wheel axel, suchthat the weight of the vehicle body may be measured from respectiveforces arising from the weight of the body being transferred to the loadsensor pins 8, 9 associated with the three weight sensor assemblies 410.

FIG. 42AA illustrates use of the weight sensor assembly 410 positionednear two connection points of a vehicle suspension device such that oneweight sensor assembly 410 is between the top of a spring and thevehicle body above, and the other weight sensor assembly 410 is betweenthe bottom of the spring and a vehicle wheel, such that the weight ofthe vehicle body may be measured from respective forces arising from theweight of the body being transferred to the load sensor pins 8, 9associated with the weight sensor assemblies 410.

A method of using the sensor assembly 410 and the components shown inthe various embodiments described above include connecting theelectronics of the load sensor pins 8, 9 to an electrical connectionpoint of the towed and/or the towing vehicle such that electricalsignals having information useful for calculating the (components) of aforce F or having information about a calculated force F may betransferred to the vehicles. The signals may be transferred by wired orwirelessly using a transceiver associated with the towing or towedvehicle. The method further includes continuously comparing thecalculated force F (and its components) to one or more ratings or limitsand outputting an alert if a calculated values exceeds the ratings orlimits. Ratings and limits may be expressed in terms of maximum values,maximum values with a safety margin, or a distribution of values, suchas a histogram, that account for inputs from other vehicle sensors andoperating conditions that affect the ratings and limits (e.g., externalair temperature, vehicle traction setting, engine performance, tirepressure, payload amount (including number of vehicle passengers), andothers.

Example

A computation for a tow vehicle is shown below:

Gwc (weight-carrying hitch rating)=12,500 lbs

Gym (Gross Vehicle Mass (GVWR)−Max Payload w/ Weight Truck)=7,850 lbsD=Gwc*(Gvm+5004.5)/(Gvm+Gwc)=1875 lbs Twc=1875 lbs Longitudinal(Aft/Fore) Loads Aft (Toward Rear):

5922 lbs (0-100 cycles)

4738 lbs (101-500 cycles)

3948 lbs (501-5000 cycles)

Fore (Toward Front):

−2685 lbs (0-100 cycles)

−2685 lbs (101-500 cycles)

−1579 lbs (501-5000 cycles)

Vertical (Up/Down) Loads Up (Toward Sky)

−296 lbs (0-100 cycles)

−454 lbs (101-500 cycles)

−612 lbs (501-5000 cycles)

Down (Toward Earth)

−3217 lbs (0-100 cycles)

−3059 lbs (101-500 cycles)

−2901 lbs (501-5000 cycles)

Starting at −1875 lbs (cycling between the loads mentioned above)

Lateral (Side to Side) Loads

Side (+/−)=790 lbs (Cycle at 1 Hz for 60,000 cycles in conjunction w/known histogram distribution)

Although certain presently preferred embodiments of the disclosedinvention have been specifically described herein, it will be apparentto those skilled in the art to which the invention pertains thatvariations and modifications of the various embodiments shown anddescribed herein may be made without departing from the spirit and scopeof the invention. Accordingly, it is intended that the invention belimited only to the extent required by the appended claims and theapplicable rules of law.

We claim:
 1. A vehicle comprising: a trailer hitch receiver configured to receive a trailer hitch arm along an axis; two magnetoelastic pins, having respective magnetic fields, configured to couple the trailer hitch receiver to a chassis, the two magnetoelastic pins disposed above and perpendicular to the axis; a plurality of sensors corresponding to the two magnetoelastic pins, configured to detect changes in the respective magnetic fields; and a processor configured to determine a magnitude and a direction of a force acting on the trailer hitch receiver based on data from the plurality of sensors.
 2. The vehicle of claim 1, wherein the two magnetoelastic pins are further configured to flex based on the magnitude and the direction of the force acting on the trailer hitch receiver, wherein the plurality of sensors are configured to detect respective changes in the magnetic fields corresponding to an amount of flex of the two magnetoelastic pins.
 3. The vehicle of claim 1, wherein one or both of the two magnetoelastic pins are configured to flex based on a vertical force, a lateral force, a longitudinal force, and a rotational force acting on the trailer hitch receiver, wherein the vertical force, the lateral force, and the longitudinal force are perpendicular to each other.
 4. The vehicle of claim 1, wherein the processor is further configured to: determine that a first pin of the two magnetoelastic pins has flexed in a first direction; determine that a second pin of the two magnetoelastic pins has flexed in a second direction opposite the first direction; and responsively determine that a vertical force is acting on the trailer hitch receiver.
 5. The vehicle of claim 1, wherein the trailer hitch receiver includes an opening configured to engage the trailer hitch arm along the axis, and wherein the two magnetoelastic pins include a first magnetoelastic pin and a second magnetoelastic pin centered on the axis.
 6. The vehicle of claim 5, wherein the first magnetoelastic pin is configured to couple the trailer hitch receiver to the chassis using a circular coupling, and the second magnetoelastic pin is configured to couple the trailer hitch receiver to the chassis using an oblong coupling.
 7. The vehicle of claim 6, wherein the second magnetoelastic pin is configured to slide within the oblong coupling in response to a longitudinal force, and wherein the processor is further configured to: determine that the first magnetoelastic pin has flexed in a first direction by a first amount; determine that the second magnetoelastic pin has flexed in the first direction by a second amount; responsively determine that the longitudinal force is acting on the trailer hitch receiver; and determine a magnitude of the longitudinal force based on a differential between the first amount and the second amount.
 8. The vehicle of claim 6, wherein the plurality of sensors includes two or more sensors corresponding to each of the first and second magnetoelastic pins.
 9. The vehicle of claim 8, wherein the processor is further configured to: determine, based on the two or more sensors corresponding to the first magnetoelastic pin, that a first end of the first magnetoelastic pin flexes in a first direction, and a second end of the first magnetoelastic pin flexes in a second direction opposite the first direction; and responsively determine that a lateral force is acting on the trailer hitch receiver.
 10. The vehicle of claim 8, wherein the processor is further configured to: determine, based on the two or more sensors corresponding to the first magnetoelastic pin, that a first end of the first magnetoelastic pin flexes in a first direction, and a second end of the first magnetoelastic pin flexes in a second direction opposite the first direction; determine, based on the two or more sensors corresponding to the second magnetoelastic pin, that a first end of the second magnetoelastic pin flexes in the first direction, and a second end of the second magnetoelastic pin flexes in the second direction opposite the first direction; and responsively determine that a rotational force is acting on the trailer hitch receiver.
 11. The vehicle of claim 5, wherein the processor is further configured to determine all directional components of the force based on data received from the plurality of sensors.
 12. The vehicle of claim 1, wherein the processor is further configured to estimate a mass of a trailer coupled to the trailer hitch receiver based on the magnitude of the force.
 13. The vehicle of claim 1, wherein the processor is further configured to transmit the magnitude and the direction of the force for display on a remote computing device.
 14. A method for determining a force acting on a trailer hitch receiver comprising: determining, via a plurality of sensors corresponding to two magnetoelastic pins coupling the trailer hitch receiver to a chassis of a vehicle, respective changes in magnetic fields corresponding to the two magnetoelastic pins, the two magnetoelastic pins disposed above the trailer hitch receiver; receiving, by a vehicle processor, data corresponding to the respective changes in the magnetic fields; and responsively determining, by the vehicle processor, a magnitude and direction of the force acting on the trailer hitch receiver based on the data.
 15. The method of claim 14, further comprising: determining that a first pin of the two magnetoelastic pins has flexed in a first direction; determining that a second pin of the two magnetoelastic pins has flexed in a second direction opposite the first direction; and responsively determining that a vertical force is acting on the trailer hitch receiver.
 16. The method of claim 14, wherein (i) the trailer hitch receiver includes an opening configured to engage a trailer hitch arm along an axis, (ii) the two magnetoelastic pins include first and second magnetoelastic pins oriented perpendicular to and centered on the axis, (iii) the first magnetoelastic pin is configured to couple the trailer hitch receiver to the chassis using a circular coupling, and (iv) the second magnetoelastic pin is configured to couple the trailer hitch receiver to the chassis using an oblong coupling.
 17. The method of claim 16, wherein the second magnetoelastic pin is configured to slide within the oblong coupling in response to a longitudinal force, the method further comprising: determining that the first magnetoelastic pin has flexed in a first direction by a first amount; determining that the second magnetoelastic pin has flexed in the first direction by a second amount; responsively determining that the longitudinal force is acting on the trailer hitch receiver; and determining a magnitude of the longitudinal force based on a differential between the first amount and the second amount.
 18. The method of claim 16, wherein the plurality of sensors includes two or more sensors corresponding to each of the first and second magnetoelastic pins, the method further comprising: determining, based on the two or more sensors corresponding to the first magnetoelastic pin, that a first end of the first magnetoelastic pin flexes in a first direction, and a second end of the first magnetoelastic pin flexes in a second direction opposite the first direction; and responsively determining that a lateral force is acting on the trailer hitch receiver.
 19. The method of claim 16, wherein the plurality of sensors includes two or more sensors corresponding to each of the first and second magnetoelastic pins, the method further comprising: determining, based on the two or more sensors corresponding to the first magnetoelastic pin, that a first end of the first magnetoelastic pin flexes in a first direction, and a second end of the first magnetoelastic pin flexes in a second direction opposite the first direction; determining, based on the two or more sensors corresponding to the second magnetoelastic pin, that a first end of the second magnetoelastic pin flexes in the first direction, and a second end of the second magnetoelastic pin flexes in the second direction opposite the first direction; and responsively determine that a rotational force is acting on the trailer hitch receiver.
 20. The method of claim 14, further including: estimating a mass of a trailer coupled to the trailer hitch receiver based on the magnitude of the force. 